Well, the diver is blowing some bubbles until either his bottle or his bottom time is used up (presuming is SCUBA and not surface supplied). The diver brought something up, which could be literally anything. If another boat pulled up beside they were probably curious about what the diver’s up to and then everyone went on their merry wa yafter a brief conversation
In other words, no one knows what the diver was up to. Except the diver. I vote for picking up doubloons from the bottom. Or a pair of good sunglasses I lost in that neck of the woods…as it were.
