Almost ** million people in the United States went swimming at least once in 2024. The majority of them did so for fitness purposes, with approximately **** million individuals indicating that they swam with this motivation in mind. Meanwhile, around *** million U.S. Americans swam on a team that year.

Registration and attendance statistics for outdoor lap swim programs. Data Dictionary: https://docs.google.com/spreadsheets/d/1WK_MaJ0Cfnmvz8y1NLv2l-LNp_OrKvyb/edit?usp=sharing&ouid=100172030647057411202&rtpof=true&sd=true To learn more about the program, visit NYC Parks website here: https://www.nycgovparks.org/events/lap-swim Note: Due to the national lifeguard shortage, outdoor lap swimming was cancelled for summer 2022 and 2023.

Over 50,000 individual level data of behaviors, illnesses, demographics from beachgoers across the United States. This dataset is not publicly accessible because: EPA cannot release personally identifiable information regarding living individuals, according to the Privacy Act and the Freedom of Information Act (FOIA). This dataset contains information about human research subjects. Because there is potential to identify individual participants and disclose personal information, either alone or in combination with other datasets, individual level data are not appropriate to post for public access. Restricted access may be granted to authorized persons by contacting the party listed. It can be accessed through the following means: Contact Tim Wade (wade.tim@epa.gov). Format: Data are stored in SAS data files and delimited text files. Codebooks with descriptions of each of the variables are available.

This dataset is associated with the following publication: Deflorio-Barker, S., D. Holman, R. Landolfi, B. Arnold, J. Colford, S. Weisberg, K. Schiff, E. Sams, and T. Wade. Incidence and Public Health Burden of Sunburn Among Beachgoers in the United States#. Preventive Medicine. Elsevier Online, New York, NY, USA, 134: 106047, (2020).

Swim Cap Market Outlook

According to our latest research, the Global Swim Cap Market size was valued at $345 million in 2024 and is projected to reach $510 million by 2033, expanding at a robust CAGR of 4.4% during the forecast period of 2025–2033. The primary growth driver for this market is the increasing global participation in swimming, both as a professional sport and a recreational activity. This trend is further amplified by heightened awareness of health and fitness, encouraging more individuals to take up swimming for its numerous physical and mental health benefits. As a result, the demand for high-quality, durable, and comfortable swim caps continues to surge, creating lucrative opportunities for manufacturers and retailers worldwide.

Regional Outlook

North America currently holds the largest share of the Swim Cap Market, accounting for approximately 34% of global revenue in 2024. This dominance is attributed to a mature sports infrastructure, widespread swimming culture, and a high rate of competitive swimming participation across the United States and Canada. The region benefits from robust distribution networks, a strong presence of leading swimwear brands, and proactive government initiatives supporting aquatic sports at both grassroots and professional levels. Additionally, the prevalence of advanced materials and innovative designs in swim cap production has further solidified North America’s leadership position in the global market.

Asia Pacific is emerging as the fastest-growing region in the Swim Cap Market, with a projected CAGR of 5.7% between 2025 and 2033. Rapid urbanization, rising disposable incomes, and an increasing focus on health and wellness have led to a surge in swimming pool construction and membership in aquatic clubs across countries such as China, India, Japan, and Australia. Regional governments are also investing heavily in sports infrastructure and promoting swimming as a key fitness activity. The growing popularity of international swimming competitions and a burgeoning youth population further fuel market expansion, making Asia Pacific a focal point for both global and local swim cap manufacturers seeking to capitalize on untapped growth potential.

Emerging economies in Latin America and the Middle East & Africa are gradually witnessing an uptick in swim cap adoption, driven by increased investments in sports facilities and a growing interest in recreational swimming. However, these regions face challenges such as limited access to high-quality swim gear, price sensitivity, and varying climate conditions that can impact swimming seasonality. Policy reforms and targeted government initiatives to promote water safety and swimming education are expected to improve market penetration. Localized demand, coupled with a rising middle-class population and greater exposure to international sports trends, is likely to boost future growth, provided that supply chain and distribution hurdles are effectively addressed.

Report Scope

Natural selection drives the evolution of traits to optimize organismal performance, but optimization of one aspect of performance can often influence other aspects of performance. Here, we asked how phenotypic variation between locally adapted fish populations affects locomotion and ventilation, testing for functional trade-offs and trait-performance correlations. Specifically, we investigated two populations of livebearing fish (Poecilia mexicana) that inhabit distinct habitat types (hydrogen-sulfide-rich springs and adjacent nonsulfidic streams). For each individual, we quantified different metrics of burst swimming during simulated predator attacks, steady swimming, as well as gill ventilation. Coinciding with predictions, we documented significant population differences in all aspects of performance, with fish from sulfidic habitats exhibiting higher steady swimming performance and higher ventilation capacity, but slower burst swimming. There was a significant functional trade-off between steady and burst swimming, but not between different aspects of locomotion and ventilation. While our findings about population differences in locomotion performance largely parallel the results from previous studies, we provide novel insights about how morphological variation might impact ventilation and ultimately oxygen acquisition. Overall, our analyses provided insights into the functional consequences of previously documented phenotypic variation, which will help to disentangle the effects of different sources of selection that may coincide along complex environmental gradients.

Methods Study organisms and general experimental design

Several sulfide springs inhabited by P. mexicana occur in the states of Tabasco and Chiapas, Mexico (Palacios, et al. 2016). For the present study, we collected young adult fish (standard length: 28-38 mm) from a sulfidic (El Azufre I: N 17.442°/W 92.775°) and a nonsulfidic population (Río Tacotalpa: N 17.275°/W 92.462°) near Tapijulapa, Tabasco, and transported them to Kansas State University (KSU), where they were housed in 80-liter tanks and given two months to acclimate to standardized laboratory conditions, irrespective of their habitat of origin. Fish were kept at under nonsulfidic and normoxic conditions, a constant temperature of 25° C, and a 12:12 hr light:dark photoperiod. Fish were fed ad libitum and had access to flake food and frozen brine shrimp twice daily. We chose to acclimate all individuals to one standardized environment, because maintaining stable H2S-rich water is difficult in the laboratory. In addition, the toxic effects of H2S lead to high mortality of fish from nonsulfidic populations, preventing factorial experimental designs where the performance of fish from different habitats is measured under multiple environmental conditions. Consequently, our experiments only quantify the functional repercussions of traits that vary between sulfidic and nonsulfidic populations, and we cannot capture potential trait-environment interactions that might impact performance of fish in their natural habitats.

After acclimation, fish were separated into groups of 3-4 individuals and housed in 40-liter tanks, facilitating the tracking individual fish across different portions of the experiment. For each fish, we quantified three aspects of performance: 1) burst swimming upon a simulated predator attack, 2) steady swimming, and 3) gill ventilation. The order of performance trials was randomized across individuals, and individuals were allowed to recover for at least one week in between trials. Fish were fasted for 24 hours prior to each performance trial to ensure they were in a post-absorptive state (Niimi and Beamish 1974; Kieffer 2000). After the completion of all performance trials, individuals were euthanized using MS-222 (500 mg/l buffered to pH 7.5 with sodium bicarbonate) for morphological analyses. A total of N=71 fish were tested.

Burst swimming performance

We quantified burst swimming performance of fish during their reflexive escape response (c-start) to simulated predator attacks (Weihs 1973; Howland 1974; Eaton, et al. 1977; Harper and Blake 1990; Domenici and Blake 1997). Fish from high-predation environments have previously been documented to perform faster at c-starts than fish from low-predation environments (Walker 1997; Langerhans, et al. 2004; Langerhans, et al. 2007), and several studies have linked burst swimming performance with survival in the presence of predators (e.g., Ingley & Johnson, 2016; Walker, Ghalambor, Griset, Mckenny, & Reznick, 2005).

Methods for the quantification of fast-start responses were adapted from previous studies (Langerhans, et al. 2004; Ingley, et al. 2016). For each trial, we placed a fish into a clear acclimation cylinder (5.5 cm in diameter) within a larger test arena (circular tank with a 40-cm diameter). To minimize vertical displacement and approximate two-dimensional escape responses, the water level was maintained at a depth of ~3 cm. After a 10-min acclimation period, the cylinder was removed, and we struck the arena with a probe (6 mm in diameter and 90 cm long) within ~1 body length of the fish’s caudal region to evoke an escape response. After the first trial, fish were placed back into the cylinder, given the same acclimation period, and tested twice more with the same procedures, yielding three burst swimming performance trials per fish. Each trial was filmed from above with a Sony NXCAM NEX-FS700 high-speed camera (Sony Corporation, Tokyo, Japan) at 120 frames per second (fps).

Videos were analyzed frame by frame using the DLTdv6 tracking software (Hedrick 2008) in MATLAB 2016a (Mathworks Inc., Natick, MA, USA) to quantify four metrics of burst swimming performance (Walker, et al. 2005) following methods established by Langerhans (2009): (1) total distance traveled (dnet [cm]) is the net distance a fish traveled within 1/12 of a second after bending into the c-shape; (2) rotational velocity (wS [°/s]) is the average rotational velocity of the head from the moment the fish begins bending into the c-shape until it has completely bent (rotational angle of bend divided by duration); (3) maximum velocity (vmax [cm/s]) is the greatest change in distance between two consecutive frames (1/120 of a second); (4) maximum acceleration (amax [cm/s2]) is the greatest positive change in velocity between two consecutive frames.For each individual, we calculated the average of each metric across the three trials.

Steady swimming performance

We quantified metrics for steady swimming performance, an energy-efficient mode of locomotion that fish use during place-holding against water flow, foraging, and mate searching (Domenici 2003b; Blake 2004; Langerhans 2008). To quantify steady swimming performance, we measured the critical swimming speed as well as swimming kinematics at different swimming speeds for each individual.

Critical swimming speed is defined as the maximum speed at which a fish can maintain steady swimming (Plaut 2001; Domenici 2003a; Blake 2004) and can be quantified by incrementally increasing the swimming speed until an individual fatigues (Brett 1964). Critical swimming speed can then be calculated as Ucrit = Uf + Us × (tf/ts), where Uf is the highest flow velocity maintained for a full time-interval, Us is the velocity increment, tf is the time to fatigue at the last flow speed, and ts is the time interval at which increases in speed occur (Brett 1964). To quantify Ucrit, individual fish were placed in a 5-L swim tunnel (Loligo Systems ApS, Viborg, Denmark), in which they were exposed to laminar flow with adjustable speed (Ellerby and Herskin 2013){Ellerby, 2013 #83;Ellerby, 2013 #83}. Trials started with a 20-min acclimation period, including 10 min without flow and 10 min at a flow speed of one body length per second (BLs-1). After acclimation, fish were incrementally exposed to higher flow speeds (Us = 1 BLs-1) every 10 min (ts = 600 s). Acclimation times and speed increments were adopted from previous studies (Hammill, et al. 2004; Oufiero and Garland 2009; Sfakianakis, et al. 2011). Trials were immediately terminated once a fish reached fatigue.

During each steady swimming trial, fish were filmed at 120 (fps) using a high-speed camera twice during each interval (once immediately after the speed was increased and a second time halfway into a time interval). Four videos were selected at speeds ~25%, 50%, 75%, and 100% of each individual fish’s Ucrit (Oufiero and Garland 2009). At each speed, we quantified five kinematic variables relevant for the hydrodynamics of steady swimming (see Langerhans, 2009; McHenry, Pell, & Long, 1995): (1) tail-beat frequency (f [Hz]) was measured as the inverse average period of ten complete tail-beat cycles; (2) rostral amplitude (R [mm]) was measured as half the distance between right and left excursions of the anterior tip of the rostrum; (3) tail-beat amplitude (H [mm]) was measured as half the distance between right and left excursions of the caudal fin; (4) propulsive wavelength (λ [mm]) was quantified as double the posterior half-wavelength; and (5) propulsive wave speed (c[mm/s]) was calculated by multiplying the propulsive wavelength with the tail-beat frequency (c= λ *f). For R, H, and λ, measurements were taken by averaging the values of each across three complete tail beats.

Gill Ventilation Capacity

Gill ventilation in teleost fishes has been described as a two-pump system, in which water is taken through the mouth into the buccal cavity, pumped into opercular cavity, and out through the opercular openings, resulting in a unidirectional flow across the respiratory surfaces (Hughes 1958). The rate at which water is pumped over the gills is consequently limited by the capacity of the first pump (i.e., the frequency of ventilation and the buccal volume). We quantified these variables for each

As of 2024, about 27 percent of surveyed respondents in the United States reported that they sometimes reapplied sunscreen at least every two hours when outside, or after swimming or sweating. About seven percent said they never reapply it.

During a May 2024 survey, it was found that gymnastics was the sport adults in the United States were most likely to watch in the upcoming Paris 2024 Olympic Games. Overall, 37 percent of respondents answered that they were likely to watch gymnastic events at the 2024 Games. Meanwhile, 31 percent of survey participants said they were likely to watch the swimming. How many events were there at the Paris 2024 events? The 2024 Paris Olympics featured 32 different sports. Aquatics and Athletics led with the highest number of events, with 48 and 49 respectively, while gymnastics included 18 events. Among the venues for the Paris 2024 Olympics, the gardens at the Palace of Versailles had the largest capacity, accommodating up to 80,000 spectators. The Stade de France, which hosted athletic events, rugby sevens, and the closing ceremony, had a capacity of over 70,000. How interested was the U.S. population in watching the 2024 Paris Olympics? According to a June 2024 survey in the United States, interest in watching the Paris 2024 Olympics was mixed. While a quarter of the population indicated they had no interest in the games, approximately two-thirds expressed a desire to watch. Nonetheless, the appeal of the games was reflected in the strong viewership for the opening ceremony, which attracted on average 28.6 million U.S. TV viewers. This figure also represents the highest viewership for an Olympic opening ceremony since 2012.