If it is the same as the CoC diver,
this addweapon "CoC_LAR7"
will add the rebreather if it has been removed.
this animate ["goggles", 1]
puts the face mask on.
You never see the fins on them, just attached to their legs (AKAIK)
To get them to use the rebreather, just start them in water, eject off a boat, parachute into water, etc...Or use the CoC_LAR7SWM vehicle and move them in (this moveindriver xxx) similar to how a parachute works.
I wrote a simple script that lets the AI swim with you which is very cool! Looks great to surface on the beach and have your team come out of the water behind you, weapons at the ready. Great addon!