I haven't done it in a pool, but yes you will need one strobe above water to trigger optically. Watch out for overheating with it out of the water. Otherwise I think you are into custom-cable territory - something from camera underwater to floating wireless trigger, or something really long from camera to first studio strobe. Alternatively consider using big video lights instead, or all underwater strobes.
Also make sure your studio strobes don't fall in and electrocute your models.
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