Except I am fairly certain the the CM's and Lifeguards have a policy against going into the water. Safe or not, it's against their policy to get into the lake - there are signs against it and since they banned swimming after the bacteria issue, they have been pretty firm on it. I might not have cited gators, but I would certainly have cited the bacteria. So if they had asked any official Disney person, I am fairly certain they would have been told no.
I agree that Disney has a responsibility to provide as safe an area for family fun as is reasonable. That includes things like fences to prevent you from jumping into a ride mechanic or climbing into dangerous areas of the park or raging dinosaurs. They take a lot of aggressive measures in this area - try walking off one of the trails in Epcot and see how far you get before someone approaches you and ushers you back onto approved paths (or ejects you from the park). they do this very well in the parks themselves.
There is a LOT of territory in the resorts and they encompass 43 square miles. It's impossible for them to patrol all of it - which is how people slip into River Country from time to time. Could the signs have been more clear? Perhaps. However, Hindsight will ALWAYS come up with more ways to explicitly say not to do something. My Hairdryer comes with a sign not to use it in the shower or a tub. However, they dolt tell me that I shouldn't use it in a pool. How much is reasonable for extrapolation?