"Full
boat" means something is completed, or can not contain anything more.
If you're told to pay full
boat, it means you pay for the complete service. Even if it's immediately cancelled, you pay 100%.
If you arrive somewhere, and told it's a full
boat, it means you cannot attend.
In poker, it means full house. It's a
bit inaccurate to call it a full boat, since there are three hands that can beat it, but you're likely to go a lifetime before seeing a "Four of a kind", "Straight flush" or "Royal flush."
From the TV show Barry, when an acting class is cancelled because of a
death.
"This class counts.
Stepping away from the class is, in itself, a lesson.
So there are no rain checks, is my point.
Okay, everyone pays full
boat for today."
In a poker
game:
"Read it and weep. Full boat"
"Hi guys, can I get a ride home? Sorry, full boat"