How can any rational person argue that the signage was sufficient to warn of a possible alligator attack? Sure, the signs say "no swimming", but most people would probably assume that is because there is no lifeguard on duty (and Disney wants to protect from liability against drownings). If you feel that you are a safe swimmer or that you there to be a lifeguard for your kids, you might go ahead and swim anyway...unless you happened to know you can get eaten by an alligator if you go in. It seems to me that Disney did not specifically include alligator warnings on the signage because it didn't want to advertise the fact that it has deadly reptiles wading throughout the property. I'm from California and, while I'm aware that alligators are prominent in Florida, I was not aware that they were on Disney property. In fact, during my last visit to WDW, I specifically noticed the absence of any alligator warnings on the signage near the various lakes on property and, based on that, asked a CM whether there were alligators on property and was told "no."
As a lawyer, I anticipate that Disney will argue that the "no swimming" signs was sufficient, but this looks like it going to result in a significant settlement.