Dive Reels, Distance line or "come-home-line" could be placed in subs and allow divers to attach themselves to it. This will allow them to come back to the starting point, specially in poor visibility environments or when exploring alien ruins.

The reel could also be allowed to be connected to a button that could retract the line dragging the diver back to the start for emergency purposes, like the diver being under attack or unconscious.

Cool idea! A drawback could be that it slows the diver's speed a bit to be pulling on the dive line.

For super bonus points, make it so that creatures of the deep can interact with the line, breaking it or even getting tangled in it and dragging the diver along behind

Slowing the diver's speed down makes sense.

Creatures or other players being able to interact with it is an awesome idea too.

So many new ways of dying too. xD
I can already imagine sinking subs dragging attached divers to the bottom with them at deadly speeds.

I'd love that idea. Maybe even have a line attached to a harpoon, so you could ride enemies. ;)

I saw some old post in which the Harpoon Gun used to actually work like one in really old builds of this game. I think it wasn't even available for download even. There were some videos too.

Harpoon guns like those could be used to drag creatures back to the sub, maybe? Perhaps there could be hunting missions or similar. I bet some researchers would pay good money for stuff to dissect.

It's true - here we are on an alien world with actual large-scale living things on it, and apparently what people are most interested in is transporting nitroglycerine

Although there are many human outposts on Europa, so it's clearly been a while since "first contact" and perhaps the scientific excitement has died down.

Even so, dragging back a sample of some of the larger and more aggressive sea creatures should be of great interest... I don't imagine the scientists often get an opportunity to look at a Moloch close up, even if it's been railgunned to death. Could be an additional mission type (as long as it doesn't become MMO-like... "Collect 17 Mantis spleens and then bring them back to me").

Here, I found the video about the old harpoon I mentioned earlier: https://undertowgames.com/blog/harpoon/

Something like this would be cool as both Dive Reels and the gun.

This is actually really fucking cool! It means that if you wanted to fix the outer hull from the outside, you could just go outside and do that with a dive reel without risking the sub sinking without you.

I'm imagining right now, a Traitor exiting the sub, following the dive reel. He has a Revolver and fires at the Reel, breaking it. The man on the reel, who only has 2 tanks of O2, struggles as the Traitor drags the reel down to the bottom of the Caverns. The Traitor enters the airlock without the diver. And when they try to find him outside the ship, the crew only find a dead crewman on the bottom floor, too late for him to be revived with CPR. TBH, I think that the Dive Reel is a good idea. Devs better get on this.

Just imagine all the possible things that could happen with this!