The reason I didn't get into the legal analysis is that it's actually pretty complicated, and it's hard to justify putting the time into analyzing it on a running message board. It would require many thousands of words to discuss the issues thoroughly, and I don't think that it would generate much useful discussion.
I will, however, try to set out a few points quickly. First, this isn't just a negligence case; in fact, some states would dismiss a claim of negligence here as a matter of law, because it would be preempted by law governing premises liability and public accommodations liability, and all of these claims have their own elements that must be established to find liability. Speaking broadly, negligence is the breach of a duty of due care, while premises liability and public accommodations liability are more likely to be expressed in terms of "unreasonably dangerous conditions" on the property. In either case, however -- whether the discussion is about the nature and scope of a duty of due care, or whether it's about the existence of "unreasonably dangerous conditions" -- the proper legal inquiry generally looks at a number of factors, of which "foreseeability" of harm is often said to be the most important, along with such considerations as the cost of mitigating the harm.
In this case, I agree with those who say that a tourist from Nebraska should not be expected to know about the extent to which alligators populate virtually every substantial body of water in Florida. I certainly didn't know that until this case caused me to look into the matter further. Although I've seen various statistics, it appears that there are somewhere between about 1.2 and 1.5 million alligators in Florida, which I've read (but not confirmed) works out to about one alligator for every fifteen people. As a basis for comparison, I looked at the number of dogs in the state. Again, different sources will provide somewhat different information, but I believe it comes out to about one dog for every five people, or three dogs for every alligator. So alligators are, from the view of this non-Floridian, remarkably common in Florida.
The flip side of that, however, is that non-Floridians appear to greatly overestimate the danger posed by an alligator. For example, there are typically only about ten alligator bites reported each year in Florida, and there had only been three or four fatalities from alligator attacks during the ten years prior to this incident. In one of those cases, the victim was a criminal who jumped into alligator-infested water while trying to escape police who were chasing him. In another case, the victim was a serial burglar who was moving from property to property during the night. In a third case, an alligator was found with remains of an identified human, but it was unclear (based on, for example, the extent of decomposition of the body) whether the victim had simply drowned and the body was later found by the alligator. During that entire ten-year period, there was only one clear case of a reasonably law-abiding individual who was attacked and killed by an alligator. (I don't recall the particular circumstances of that case, but I do remember that the victim was an older man.) In total, it suggests roughly one alligator bite for every 150,000 or so alligator years, and one fatality for every several million alligator years. And although there have been some fatalities from alligator attacks on small children during the past forty-plus years of recordkeeping in Florida, those attacks are still a small minority of the total number of cases.
It's important not to push certain analogies too far, but it's interesting to compare some of those statistics to other dangers, such as dog attacks. With about 70 million dogs in the U.S. and about 35 fatalities and many thousands of bites from dog attacks each year, alligators -- despite their frightful looks and reputations -- come out rather well by comparison, perhaps because they tend to avoid humans (except those who insist on feeding them). Although alligators are not precisely benign, they are also not particularly dangerous when compared with other common sources of risk, even in areas where their population is quite high.
Of course, even where the probability of harm is extremely low but not, as a matter of law, "unforeseeable," other factors must be considered, including the cost and efficacy of preventative measures, which in this case might have been nothing more than a sign warning about alligators. At the same time, there are costs to providing warnings of extremely unlikely events, including (among other things) sub-optimal decision-making by people who may give too much or too little credence to particular warnings. You can see that a lot in products-liability cases, where products often have so many warnings that a consumer cannot effectively distinguish between those warnings that are worth paying attention to and those warnings that are simply the result of rather cynical lawyerly efforts to provide defenses against future legal claims.
Although I am emphatically not taking a position on the merits of the various arguments in this case, I do believe that it would not be unreasonable for a careful analyst to conclude that, in the particular circumstances here, the likely existence of alligators in that body of water did not constitute an "unreasonably dangerous condition" of the property, and did not give rise to a duty of due care that encompassed warnings and other measures to lessen the probability of alligator attacks. That the victim here was an invitee at a place of public accommodation probably heightens the standard of care on Disney's part, but that's not, in my view, conclusive as a matter of law.
One interesting sidelight is whether the imposition of a duty to provide a warning about alligators could be justified on the grounds that, even though the warning refers to a very remote risk, it might be more effective than other types of warnings to mitigate more likely risks of entering the water, like risks of injury or death from microorganism infection, drowning, or lightening strikes. I think that most people agree that a simple "No Swimming" sign probably doesn't provide the same deterrent effect. Putting up signs about alligators merely to lessen the incidence of much more common risks seems a bit dishonest, but it's an interesting idea.
By the way, none of what I've said suggests my views about what a lay jury would do with this case. Although I think that I would feel comfortable arguing to an appellate court that the trial court committed reversible error in finding negligence as a matter of law, I would dread the prospect of telling a lay jury that the mother and father shouldn't be given a penny in their lawsuit against Disney. I am not in some sort of academic or intellectual bubble with no understanding of how ordinary humans think, feel, and react.