Burying uncle

Bubbles and Barbie, two blonde sisters had promised their Uncle, who had been a seafaring gentleman all his life, to bury him at sea when he died.
Of course, in due time, he did pass away and the two blondes kept their promise.
They set off from the beach with their uncle in a burial bag and loaded onto their rowboat.
After a while Bubbles says, 'Do you think we're out far enough, Barbie?' Barbie slipped over the side and finding the water only knee deep said, 'nope, not yet Bubbles'.
So they row a little farther.... Again Bubbles asks, 'Do you think were out far enough now? Once again Barbie slips over the side and almost immediately says, 'No, this will never do, the water is only up to my chest.
'So on they row, and finally Barbie slips over the side and disappears. Quite a bit of time goes by and poor Bubbles is really getting worried when suddenly Barbie breaks the surface, gasping for breath she says, 'OK, it's finally deep enough. Hand me the shovel.'