Knock on the hatch.
with a woofie.
Because they don't like random people knocking on their doors
Swim down and knock on the hatch. (In Sweden we have a running tradition of telling jokes about stupid norwegians. They do the same about swedes)
Knock on the door.
Cyborg Bjorn Borg hosting smorgasbords at the morgue.
Pork! Pork! Pork!
Bless you!