Posted on YouTube without description, via Reddit, where commenter VikingMart identifies the location as Anegada in the British Virgin Islands.
The local fishermen that dive conch throw away their shells here most of the time. With the amounts that they dive and have dived up, its probably a good idea since having a bunch of conch shells scattered around everywhere could be an eyesore.
These shells aren't as pretty as you probably think they are. Most of of them are defaced. This is because in order to get the conch meat out, fishermen usually make a hole by the "nose" of the shell. This is to reach and loosen the snail muscle (with a screwdriver or knife), and then pull it out. This leaves these conch shells defaced and one would probably have a hard time selling them.
Based on VikingMart's description, I think I found it on Google Maps:
