What are the hydration requirments in swimming?

I could imagine needing to drink if it a 5K+ swim in 80+ degree water. Indeed, the only 5K I have ever swum in which I drank water (other than unintentional gulps of the venue) was in a lake that was probably 82-84F. The race was 3 laps, and the race organizers positioned someone at one of the corners with drinking water and cups. No other OW swim I have ever swum (all 5K or shorter) has offered an aid station, although some allow personal kayak or paddleboard escorts who can supply food or water and others have involved laps starting and finishing near a beach where a person could have taken a small detour for a drink or snack. The critical factor isn't the distance so much as how long you are going to take to complete it. At my speed, the performance advantage of drinking or eating during a 5K would not be great enough to outweigh the hassle of consuming the food or water. If I were doing an event that was going to take me 2h or more, though, I would feel different; in that case, I might make sure I had either a paddler or the opportunity to go up on the beach to grab a drink or bite between laps.

I could imagine needing to drink if it a 5K+ swim in 80+ degree water. Indeed, the only 5K I have ever swum in which I drank water (other than unintentional gulps of the venue) was in a lake that was probably 82-84F. The race was 3 laps, and the race organizers positioned someone at one of the corners with drinking water and cups. No other OW swim I have ever swum (all 5K or shorter) has offered an aid station, although some allow personal kayak or paddleboard escorts who can supply food or water and others have involved laps starting and finishing near a beach where a person could have taken a small detour for a drink or snack. The critical factor isn't the distance so much as how long you are going to take to complete it. At my speed, the performance advantage of drinking or eating during a 5K would not be great enough to outweigh the hassle of consuming the food or water. If I were doing an event that was going to take me 2h or more, though, I would feel different; in that case, I might make sure I had either a paddler or the opportunity to go up on the beach to grab a drink or bite between laps.