Another word for condom.
Make sure you get in a lifeboat before the ship sinks, hehe.
The more usual definition of lifeboat is a boat usually stored on ships or deployed to rescue those in trouble at sea.
Boats stored on ships are used for passengers and crew to escape from a sinking ship, or perhaps to rescue someone who has fell in or been found in the water.
Harold: I say old chap, do you have any lifeboats to spare? I am wooing Doris tonight!
Jack: Harry, I'll give you a lifeboat if you stop talking like that.
Captain: Good lord, we're sinking! Get everyone into the lifeboats now!
First Mate: Sorry sir, we already deployed the boats to rescue Mr. Creosote...
Captain: Seven boats for one man? Are you insane?!?
First Mate: He's kind of fat...