The hot tub has been leaking noticeably lately. I called the repair guy on Monday, and he finally had time to make it out today. Looks like the pump is improperly sealed. It's possible that things will be fixed in time for the party (I'm waiting for a call back after he checks for parts with his distributor)... But it's also possible it won't. Since just letting this sit would very quickly change this from a $400 repair bill to an $800 repair bill, the tub is currently drained and he took the pump motor with him.
Guess I'll find out shortly whether we've got a hot tub for this one.