Pretty self-explanatory, I think. I mean, I don't mind having to resurface after some time, but lessen the 2 hour wait to like 2 or 20 minutes or something like that. Then again, if the need to resurface and the depressurize can become nonexistent, I won't complain.

You can do it yourself.

Start S3PE, put "scubad" in the name filter and activate the filtering (ticking the checkbox
on the left of the Name textbox, the checkbox called "Filter Active" and clicking the "Set" button).

Open GameplayData.package, right click on the _XML resource called "ScubaDiving_0x11..."
and export it into a new package that you'll put into your Mods/Packages folder (preferably
into a sub-folder for things you still have to test before consider safe/stable/working) using
a meaningful name like ScubaDivingTuning.package.

Now open the newly create package (with S3PE) and edit that resource (right click + Notepad)
to your liking changing the values in the fields (read their description and you'll be fine).

You can select the duration of the diving, the cooldown before the next one and other stuff.

Once done with the editing, save the file, close Notepad, commit changes and save the package. Test in game.

Be careful if prolonging the duration might increase the chances of drowning (I don't know that EP well, just saying).

You can get your Sim the 'Lungs of Steel' lifetime happiness reward, it might be 15,000 happiness points. I get that ASAP for my divers because they can scuba dive indefinitely without having to surface. You can also wait until they surface and then cancel the depressurize moodlet in their panel, they'll then be able to dive right away.

I don't have S3PE, so I can't, and the download no longer works.

All right, thank you so much for the tip.