Yeah the UI did end up a bit rushed without much explanation. If you got stuck on that attatchment screen, what you were supposed to do is place the attatchment on one of the green spots on the sub.
The return to shore button there is a bit of a funny story, we realised last minute that you could get softlocked if there was nowhere left to put the attatchment when that very almost happened to me while testing, so we decided to add a give up button. The problem was, the person making the UI graphics wasn't able to help at the time so I had to just use the best already existing button available, which was return to shore.
How did you manage to have 2 layered menus? Do you know which menus they were?