Are there any official underwater rules (not the basic few paragraphs in the corebook) that cover weapons operations, explosions, expanded combat, maybe some vehicles?

if so where?

If not, if you've done any undersea adventures I'd like to hear your house rules.

Strongholds of Resistance has a couple of submarine vehicles, a portable underwater torpedo launcher and an organic gill, and there are a few species with the Amphibious or Swimmer abilities. I think you just combine whatever the rulebook says plus appropriate Athletics checks plus Setbacks as needed. The breath mask/respirator gear is your diving equipment.

The books haven't gone into whether or not weapons work underwater. Older EU sources says blasters and lightsabers don't work normally, TCW seems to imply that they do. Pick on you like more (I can offer a little advice for the former option, if you'd like).

Also, try to add rules from gravity, may fit

I remember from TCW series that lightsabers work underwater just fine (for some reason) but I am not so sure about blasters, didn't the clones used different weapons when they went to the Mon Calamari homeworld?

I remember from TCW series that lightsabers work underwater just fine (for some reason) but I am not so sure about blasters, didn't the clones used different weapons when they went to the Mon Calamari homeworld?

Oh thats right! I have to find that episode. thanks!

For my group, one of their stops is going to have intrigue underwater, we are going to play it that unless the equipment has been modified as such, electronic weapons and equipment wont function the same underwater. I think it is believable that an amphibious jedi would have an amphibious lightsaber, but I don't think all lightsabers would work "just because". I also want my players to think around the situations instead of just "rush. stab, pew pew."