Yes, there are two or three dive shops there just past the lagoon.
A couple of things, though...
Although the park is open until 6 or 7 pm, the locker room closes at 4:30.
They won't let you dive unaccompanied there any more. Seems some gringo stupido got lost out there recently and had to be rescued. Tank & weight rental is US$16 (IIRC), which includes a DM fee for babysitter. Our guy was real nice about it, though, even apologetic.
They won't let you take lights into the water, because of the temptation to go further back into the caves than would be prudent for those of us not experienced in such environs. Again, some of have screwed up and made this necessary.
All that said, the dive there is worth doing. The cave vestibule alone with the glassy slippers (I believe that's what they are) and the big tarpon is worth the price of admission.