Combat side stroke or CSS is a variation of the side stroke that was developed by and taught to the United States Navy SEALs. The Combat Swimmer Stroke was developed for the United States Navy Seals by Former Navy SEAL Stew Smith (CSCS) and Terry Laughlin of Total Immersion Swimming. [citation needed]
The combat side stroke is a relaxing and very efficient swim stroke that is an updated version of the traditional sidestroke. The CSS is a mix of sidestroke, front crawl, and breaststroke. The combat side stroke allows the swimmer to swim more efficiently and reduces the body's profile in the water to be less likely to be seen during combat operations if surface swimming is required. The concept of CSS has been that it can be used with or without wearing swim fins (flippers), the only difference being that when wearing swim fins the swimmer's legs will always be kicking in the regular flutter kick motion without the scissor kick. This stroke is one of the strokes that can be used for prospective SEAL candidates in the SEAL physical screening test (PST), which includes a 500-yard swim in 12 minutes 30 seconds to determine if the candidate is suitable to go to the Basic Underwater Demolitions/SEAL school.