Mark your space
Mark it once. Every card in marathon swimming (open water) starts from this space and adds what it needs.
The space
A pool with a lifeguard for the pool-based cards; open water only with a coach, an escort or a safety boat, a tow float and a bright cap.
Where it fits: supervised pool; club open-water sessions.
Kit
Goggles, a bright cap; a tow float and a wetsuit if the club requires it.
Safety
Never swim alone; a buddy system and a head count; a defined swimming area marked with buoys or rope floats; rescue aids ready (a pole, noodle or rope with a float, or a rescue tube or board where there are waves or currents); highly visible swimwear, and a cap when hair could be a hazard; ask the local council whether the water has known contaminants such as blue-green algae, or hazards such as stonefish; in cooler water shorter swims and wetsuits; leave the water for poor visibility, extreme temperatures or thunderstorms; no breath-holding or underwater games.
awiseathlete.com/sports/marathon-swimming/setup