maybe this can be arranged at some summer day with a pool...
Certainly one would mostly need a set of full-face-masks (otherwise one runs the risk of loosing the regulator out of the mouth and that has a non-zero risk of drowning/asphixiation [and not the breathplay kind] and we certainly don't want that!) and likely setup either some extra long medium pressure hoses to an external air tank or have some regular tanks mounted on / lying next to the participants.