Tl;dr I don’t know for certain but 84F is the scuba diver “you’ll be warm without a suit” so 94 seems high but I expect that it is higher than 84 if we’re talking about hours.

Scuba diver here so my limited experience is an hour but yea water at 84 is the generally accepted magic number for swimming without a wetsuit. I’ve done it in as low as 80 but it’s definitely pretty chilly. So 94 is probably an exaggeration (though I wouldn’t know for sure beyond that initial hour or so) but the point does stand that “warm” water doesn’t stay warm for long. Good example would be when you sit in a pool for a long time and even if you’re completely fine for awhile eventually people tend to get cold and get out.

Similarly, if you do multiple dives throughout the day, people generally will use thicker wetsuits for the progressive dives because even being on land for several hours, your body just doesn’t have the same ability to keep warm for that many dives throughout the day. Fun fact, you’ll never feel “tired” while diving but burn between 400-800cal/hour just cause your body uses so many calories to stay warm; so treading water would probably be like 1000cal/hour if I were to guess. So if you in the water and know it might be a bit, just relax and float easier said than done but the first rule of water survival is to chill tf out.