Most are out of your price range.
Turks has excellent snorkeling but it is out of your price range and no nightlife.

Snorkeling is average at St. Lucia

Caymans are not lush, and probably out of your range.

Caneel Bay completely out of your price range, other than that would fit everything else.

Bahamas just okay snorkeling (unless you go to Andros, which is out of your price range and no nightlife.

So you're left with Cozumel, which fits everything you want perfectly!

i have to agree with blamona. t&c, gc & caneel very pricey. (otoh if expedia will book you caneel for $200/nt book a room for me too) st. lucia is too far for 4 days.

you might like isla mujeres. it's another small island just off cancun. good snorkeling & diving but a bit "sleepier" than cozumel. it's small & everyone gets around on golf carts. bars are small but fun & pretty much all in one area.

would you consider renting a villa on the maya riviera (coast south from cancun to tulum)? you could get something wonderful with 4 bdrms en suite for much less than $800/nt. most come with daily maid service & some have cooks available if requested. this is just a sample -i've never been to this house http://www.locogringo.com/akumal/balam_ek.htm?ID=797

or rent condo/s? in akumal
there's an ai in akumal that might fit your budget akumalbeachresort.com has snorkeling off beach & you can walk into town on the beach in 10 mins.

you'll have better access to stuff to do if you're on the mainland rather than isla mujeres or cozumel. ie: ziplines, atv jungle rides, shopping, seeing cenotes, tour ruins, water parks > www.xcaret.com & www.xelha.com

Is your budget $200/night per person or per couple? If it's per couple I'm afraid I have to agree with Blamona - you are going to find it difficult to get everything you want at that price.

I guess I should have added a budget per se. Booking through expedia all those places are within a couple hundred dollars per person of each other since I'm only booking a 4 night stay.

Hope that helps.

My 2 favorite places to snorkel is Grand Cayman and Cozumel in that order. We've been to Cozumel 4 times. The last time was December, 2009 right after a tropical storm. That area has been hit so many times in the last few years with tropical storms and hurricanes that the snorkeling has become a little iffy.

We have stayed at the El Coz and it's a great hotel for what it is. The rooms are amazingly large and most (even the lowest catagory rooms) face the ocean, which is rare in any other destination. The food is a little so-so. The menu items are better than the buffet.

Chanakaab Park was great for snorkeling with a full service restaurant and bar with beach chair service. There are also beach clubs with snorkeling. Though you can techincally snorkel from the beach, many entries are rocked iron shore. A little difficult to get in and out. In the main area of San Miguel, to enter the water is by ladder. Though somewhat inconvenient, it does make for better snorkeling than sandy bottoms.

We have been to Grand Cayman twice. The Sting Ray Excursion in Grand Cayman has to be THE BEST snorkeling I have done to date, and we've been to many destinations. There were 2 stops before swimming with the Sting Rays. The clearest water, the healthest coral and the most abundance of fish and other sea life. I bought the video of our excursion and it is just so awesome. We also snorkeled the Wreck of Cali off of 7 Mile Beach, which was good also.

The second best snorkeling was the Sian Kaan Biosphere outside of Tulum, Mexico. That area has not been hit as hard with tropical storms and hurricanes like the Playa del Carmen area. It is a tour because it is about an hour outside of Tulum and then 1 1/2 hours down a bumpy dirt road and then a 30 minute boat ride. It was so worth it though.

St. Lucia's snorkeling was basically non-existant. The water was too dark to see anything. Our trip, it rained every day, which just stirred the water up.

Though T & C has Grace Bay, which is an awesome beach, we find the snorkeling as good as Grand Cayman. We didn't find much snorkeling in St. John or Nassau either.

If your budget will work, I would go with Grand Cayman. If not, than Cozumel is a great second choice.

If you're interested, I have all our travel pictures posted including our underwater snorkeling shots at:

http://community.webshots.com/user/kvrlvn

Correction:

Though T & C has Grace Bay, which is an awesome beach, we didn't find the snorkeling there as good as Grand Cayman.

I can only comment on T&C we stayed at Coral Gardens (there is a trip report some where her on Fodors) and I spent most of my time circling the reef that is directly outside the resort - although many of the rooms are privately owned (freakily the one we stayed in was owned by my dermatologist) so the standards vary.

I'd go back for the snorkeling or the beach but we were done with the island after a week..

Ha! found the TR from our visit in 2005.
http://www.fodors.com/community/caribbean-islands/trip-report-tc-august-2005.cfm

My three (areas) that I think have the best shore snorkeling are as follows:

St John....a jeep rental is a must. 40+ beaches to explore. Very safe to venture all over the island on your own. Some fantastic snorkeling opps at several different beaches. The better stuff is usually a 100-200 yard swim off the beach.

Akumal (Riviera Maya)....there are plenty of condos or villas to be rented for a decent rate. The reef in Akumal bay is excellent, and tons of turtles!! A great laid back area.

Grand Cayman....tons of choices of condos or hotels right on 7MB. The reefs in GC are also excellent. The island itself is flat & scrubby, but the restaurants are world class, although pricey at times. Another very safe island to venture out on your own.

Personally, I think the best bang for your buck is Riviera Maya. St John & GC will not be cheap, even though I liked the snorkeling better.

totally agree with the suggestion to get a 4 br villa along Riviera Maya or in Cozumel. Should bring you in under budget in great accommodations.

For "off the beaten path", local color, good snorkeling, and reasonable prices, you might consider the island of Culebra in Puerto Rico. It is only about 18 miles or so from St. Thomas so the scenery is something like the USVI but a bit more arid. good info at www.islaculebra.com

Read Bufftiger's recent report about snorkeling in Culebra ("Puerto Rico/Culebra Trip Report".

Checked out the Mayan Riviera based on the discussion in these comments. Thanks to @fishee for the suggestion to look at villas -- was shocked how affordable they can be! (Wasn't expecting that, but hey... haven't visited MR before.)

For instance, here's a 4BR on the beach with (apparently) good snorkelling right offshore. Only $329/night for the WHOLE VILLA. Price seems to hit $500 in high season.

http://demeure.com/properties/villa-cascadas-akumal

Not sure how close this is to night life. Anyone know what the snorkelling is like in this area?

Nice place -- it appears to be near the end of Akumal Bay which is where I've heard the good snorkeling is located. People often discuss Akumal Beach Resort as having great near shore snorkeling and that looks to be several miles South of your location.

Hopefully, someone familiar with the area can chime in but in the meantime, I'd suggest looking at a map and reading reviews of whatever hotels might be closest to this particular villa. Reviews will always comment on good snorkeling if it's right off the beach.

Snorkeling is great in Grand Cayman as so is diving. Most people rent condos,a 2 bedroom condo can be rented for about $300 per night. Usually this time of year they throw in a free night if you stay for 5 or 7 days. there is a little nightlife and very good restaurants in all price ranges.

We went to Playa del Carmen (Riviera Maya) last December and it was a fabulous trip. Snorkeling was great. Lots of places to stay for all budgets. The town of Playa is very fun with lots of good restaurants and shops and nightlife. Would highly rec.

sorry I didn't see your email sooner, found it while I was looking for great snorkeling beaches in Negril!! Highly recommend Aruba, best beach snorkeling ever! our resort's private beach offered snorkeling people were paying for!! I saw all the fish I'd hoped to see there...definitely a must for snorkeling fans!We stayed at the Renaissance Marina Aruba (Adults only)...compared to previous resorts we've stayed at in Carribean, nightlife leaves much to be desired but the private beach, snorkeling & the food made up for it! Best beach so far for our vacations in Carribean!

Wow Renee,

That's the first time I've ever heard anyone recommend Aruba for snorkeling. Not sure where you have snorkeled in the Caribbean, but I know that Aruba is not known for snorkeling. And also kind of surprised that you couldn't find any nightlife in Aruba either....there are casinos & clubs everywhere down there. Did you get away from your resort?

yeah Bassguy, I was really surprised by all that we saw right on the resorts private beach...as for the nightlife, we did go off the resort a bit but not as much as we usually do and we weren't really in the livelier nightlife area like the resorts up the road that are known for a better nightlife...I'm just used to being in resorts with better nightlife and probably should have ventured a bit more but we were on our honeymoon so had a really good time...If I do go back will definitely check out resort nightlife next time...never been an issue before, but like I said, overall it was a really good spot.

Renee,
If you thought the snorkeling in Aruba was great, try Grand Cayman, St John, Cozumel, Riviera Maya just to name a few. Pretty sure you might be blown away at these locations after snorkeling in Aruba...