Well, a great many people will say that, eventually, there's a point at which the PCs die, even if that is uninteresting. It isn't like the OP had the PCs killed instantly. How many boats do you send them before the flood overtakes them?I think that many in this thread are too focused on "what's realistic" (read: what's likely) as opposed to "what's interesting".
Is having PCs die inherently uninteresting?But generally speaking, I have to go with what's real....the people playing the game. My decision has to take that into more consideration than the fiction. Especially since with fiction, you can come up with any number of outcomes that could be considered "realistic".
There's been a lot of talk here about relying on mechanical resolution. Sometimes mechanical systems make it so a character dies. Proponents of strictly holding to system will argue that result is not inherently more or less interesting than any other result.