You could do it without a suit, there are usually swimmers in the shallow cove. But if you have a suit, even a 3 mil, you will have a much better time of it. The vis is offten marginal, and there's alot of area to cover. By the time you get done you'll be pretty cold, and bumping along the walls you might get dinged up some.
100% agreed.
And just to add another reason to wear the suit, there have been quite a few jellyfish around lately.