The nearest fountain is the one just off the Skeleton Key stairs on Level 9,
the Rat Level… if you've opened the SK doors on levels above where you are,
it's fairly easy to get back to water… luckily the regular stairs down to
Level 12 (the Knights Level) are right near where the SK stairs open out on
Level 11, so you can get back there without having to get alllll the way
through the Knights, Spiders, etc…
Remember, "empty flasks" can be filled with water too…!
BobR