1. I wouldn't be swimming if my seizures were that severe. I have complex partial seizures and am somewhat unlikely to drown.
2. I would not take my service dog in swimming with me in a pool. I think it an unreasonable accommodation because the fur would damage the filtering system. I was a little surprised about this being an issue at a lake. However, when they pointed out concern over rescue attempts and how the dog might interfere, I can kind of see their point.
The next question is how good is a GSD at water rescue? I'd be rescuing Cole because he has negative buoyancy, which is a common enough problem with working GSDs. I think Ruby might pull it off if I was in a position to help a little (ie hang on to her tail or something). Luna (who has generous fat) could physically do it (if I held on), but would she bother? In my mind, the real question is whether the dog could actually handle her having a seizure in the water. I think even a PWD would have difficulty with that, if they are severe seizures. Given a choice between a human lifeguard and a dog lifeguard, I'll take the human.