I dove in Juan Dolio a few years ago.  It was OK, not spectacular.
Only did morning dives, waves to choppy for afternoons & nights.

It sucks..........period.

The Punta Cana airport installed a scanner recently.  Security sits nearby
and confiscates articles not allowed on the flight home.  This spring they
confiscated two packages of AA batteries.  I asked them why. They pointed to
a picture of a paper wrapped battery from the 1960's with a post in the
center and side that you attach wires to.  Of course they didn't want the
battery packs that only fit in the camera - just the ones that fit
universally.

This site is good for DR news.
www.dr1.com

Try the fresh water diving if you get a chance.

Just got back from 2 weeks at Iberostar Dominicana near Punta Cana.  Did a
total of 8 dives with outfit at the hotel called Dressel Divers.

Can confirm what others have said that it's a bit boring.  Very little
wildlife and the coral tends to be mainly brown.  That said, there were a
few highlights.  We did a trip to Catalina Island off the South coast.  The
wall (more of a slope really) wasn't that good, but "The Aquarium" dive was
very good.  Also near Punta Cana are 2 reasonable wrecks.  The "Amstrong" is
relatively recent and can still be seen above the surface about half a mile
off shore.  A bit further away is "Monica's Wreck" which is older and has
spread rail tracks across the seabed.  Many good swim throughs as well.

Cheers

David B

   The area I was in had little sealife and WAY to many go-fast boats.
If you really want to dive there's one thing to be damn careful
of............the pork. When I was there a year or so ago there were a
BUNCH of people sick, myself included, and it didn't seem to be
relegated to a particular hotel or quality of hotel. The topless beach
was top notch however.