Scuba Diving Glitch

I have the same problem, just started happening (worked before). No mods ever. ResetSim didn't work. 

I'm thinking it has something to do with Into The Future. Been some godawful glitches since that one was installed. 

Is it just one Sim or all of them ? Did you try moving him out and back in ?

It's my first time sending my sims to dive in the sea since I got Back to the Future, I have seen with my own eyes that they have been able to go diving in my game...

But this whole problem happened to me as well, and I have tried all the steps here; resetsim doesn't do anything else but send my sim back to shore. Making him swim back to shore and then out again doesn't help either. 

I use the testingcheatsenabled code a lot, and the only way I could get them to appear under water was to make them teleport there, but they would only start walking around on the bottom of the ocean instead of swimming around, and they're able to open sea chests (with some messed up swimming animations), but then they go back to walking again.

I really hope there will be more sollutions!