Looking for something similar...

[Randi Rabbit]

... but easier and not reliant on co-op. I like the side on aesthetic and management of this game, I actually have Thalassophobia and can't play games like Subnautica (they're too real man) but surprisingly Barotrauma didn't freak me out, maybe it's the side on aspect apposed to being completely surrounded 360 degrees by vast open ocean. I don't get on well with random players as I'm very particular and like to take games slow and methodically, which I know isn't possible here, hence why I'm looking for something like this, but not this. Any Recommendations?

[Beltneck]

Game has sandbox options, just make it easier.

Can even make the game easier with some automation and a bit of ship design.

Like I made a circuit that always keeps reactors at the most efficient burn rate for the current load, and automatically shuts down if there is a problem. Relays that disconnect equipment from power when not in use, just to save a bit more power. Fire suppression using small pumps to partially flood rooms. Automatic discharge coil when monsters get close to my hull. An alarm system that notifies chat what kind of problem is happening and in what room. Drones I can control from the sub to clear caves before I go mining. The kind of stuff you can do with circuitry is one of the best features of this game.

Can pretty much run my whole sub with just the starting crew into the mid campaign. They do repairs and drop things in the right containers, I collect resources and navigate, then automation takes care of the rest.

[Asclepiust]

The only game lve played and with this kind of gameplay be FTL.
But it even harder..just change settings in this game(barotrauma) and it suits you well
UPD:if you need ocean experience similar to subnautica => farsky (thalassophobia might be a problem there)

[Bookslayer10]

This game isn't reliant on co-op, you can do a pure singleplayer campaign where you just control an entire crew of bots. There's also plenty of options to make the game easier in the settings, like increasing crew health, fuel capacity, mission payout, etc. Singleplayer lets you go as slow as you want, I've played SP a lot and sometimes I take over 2 hours on a single level because I want to loot every single cave, ruin, and wreck.

[Russian Sly]

Void Crew

[Kairi ♡]

We need to go deeper, if you want essentially simplified version of Barotrauma.