When diving with my cousin a couple years ago in Key West with Southpoint Divers, we were heading back to the pier. We happened upon a couple divers sitting in the middle of nowhere, miles from land. They had been dropped off to do an advanced dive while the rest of the boat went to a different location. Our crew refused to let them sit and wait, and pulled them onboard. We then drove them to their boat, which was quiet a distance away. Would anyone here knowingly let their boat just drive away while they were underwater? I certainly wouldn't.
I would think that would be negligence!! I would find out what company that was and NEVER dive with them!!
If a dive operator said, 'Hey, we're gonna drop you off and pick you up later...' I'd tell them where they could stick their snorkels...
If the divers agreed to picked up later, they are more advanced divers than I'd care to be...
I might replace "advanced" with another adjective.
A few years ago on a trip to Playa Del Carmen the dive shop attched to our hotel (i forget the name) offered to do that very thing. They had a group of snorklers to take out and a group of divers from Germany. Their idea was to drop the snorklers off near a point about two miles up the coast and then take the divers to another location. When all the divers were back on board...then they would return for the snorklers. Admittedly the snorklers could go in to shore and wait (in a perfect world) but what if there was an emergency?
Many of the group went and returned without mishap, but the what if's should have made a bigger concern for the dive shop than it seemed too.