Bar Talk 2

Sitting in the ship’s bar one night, surrounded by philosophers, Dick McGill expressed the opinion that, were the oceans to be drained, the major shipping routes of the world could be traced by the litter of beer cans on the ocean floor.
“You’re full of shit” opined a particularly subtle and suave listener “beer cans don’t reach the bottom. They reach a level where the water is so dense that they can’t sink any deeper”.
Visions of millions of beer cans, suspended beneath the waves, swam before our eyes.
“No they don’t” said another Einstein “because they would fill up with water as they sank and then they would weigh more.”
“Yes, but the water which filled them would be from the surface and be less dense, so they would pop.”
“Nah, there would always be some air trapped in them and so they’d float at a certain level.”
“How the hell could they float if there was no water left in the ocean?”
Deep silence reigned for a moment then someone said:
“Whose round is it?”