Deep sea fisherman - Prison - Envelope
Initial idea:
A man in prison a prison cell, a guard walks up to him and says "You have a letter." and then guides him out. Every open cell they pass shows a clip of the man's life, including him working and ending with the act that got him incarcerated, pushing someone he works with into the ocean and then they do not surface? He end up led to a room with the envelope and other guards are stood around muttering about it.
Then it ends with the man opening the envelope with a shocked look.
Idea #2:
On a floating island community, deep sea fisherman receives a letter with specific coordinates as his next place to fish and gets on a flying boat to the turbulent ocean well below the islands, no land anywhere in sight. He and his crew start setting up to fish, lodging heavy duty rods into ports and starting to bring up large nets, emptying and lowering them again. One of the nets contains a mermaid, the man wants to free it, another crew member wants to keep and sell it on the black market, they argue, it gets physical, the man pushes the other who slips, hits their head and falls off the boat. Crew tries to get them back up but they don't see them again, crew heads back to the island and the man willingly submits to imprisonment.
Idea #2, alternate ending:
Mermaid is brought up in the net, the crew release it but the man is captured under its thrall and jumps into the ocean to join it. The man swims after the siren through odd shoals of fish and coral structures, ignoring his need for breath until it gets too much, siren then grabs him and drags him even deeper as he passes out.
Idea #3:
Man in an underwater base/giant glass dome type thing with all the lighting being a soft pulsing red, he gets up, he gets ready, he has breakfast, he walks to a room with a hole in the bottom into the ocean and grabs a fishing rod, he fishes for a bit and catches a few odd creatures before one of those cylinder things in those pipes thunks down, he rushes to it and pulls a sheet of paper from it that says "I'm sorry, you're on your own. We still can't come and rescue you." He sighs and returns to fishing.