Remove the case back and grease the o-ring. Since you have it open, remove the crown and grease the crown and tube o-rings. Put them back and check that
The crystal is well setted. If it is, then have it pressure tested up to 10atm if you can, if it pass......go swim with it!
My experience with Rolex reps....they are always good for swimming after greasing, except the Daytonas! The only leak I experienced is wt a GMT iic, but it was due to improperly
Setted crystal.
Good luck.