Tobago
If you are adventurous, like drift diving, and looking for a mellow, affordable, uncrowded dive trip both in the water and topside, Tobago may be your answer. Out on the edge of the Caribbean and just miles from South America this island provides a much more authentic experience than many of its neighbor islands to the north.
Its worth a couple days checking out Trinidad, and I would recommend catching a steel pan performance and grabbing a Bake'n'Shark sandwich on the beach in Maracas Bay. There are some sketchy areas of town, but in general I think Trini is safe, I had no problems. Take the usual traveling precautions. Also, if you are a coffee drinker, be sure and pick up some here from the store (or any other necessities) before heading over to Tobago. Tobago stores just carry basics and there's not much near the dive areas. Take the ferry over from Trini and if it's a weekend you're likely to encounter locals partying it up on the ride over.
The difference between Trinidad and Tobago are night and day! While Trinidad is developed, bustling, and noisy, Tobago is just a completely tropical natural island with a small population. Gorgeous views, waterfalls, hikes, beaches. Very, very mellow and very safe.
Dives - Highlights are the worlds largest brain coral, at least one good wreck dive, and lots of big animals. Among the latter we saw plenty of nurse sharks, 6.5 foot reef shark, manta rays, eagle rays, moray eels, Grouper, and a school of big Tarpon! Most of the dive boats are small because most of the dive sites are just 10-20 minutes away. You'll be diving in groups of 6 and probably be the only boat out there! The remote island location provides lots of current and great drift drives in particular the site called Flying Manta, where you fly through a coral canyon. Water temps are always warm, coral in good condition and visibility good.
Unfortunately I had not really picked up underwater photography yet back in 2008 on this trip. I had a disposable with me but to post those is a little embarrassing at this point.
Topside in Tobago: eat, chill, and hike. Birdwatching is big too. That's pretty much it. Not a lot of nightlife. My mistake was I did this trip by myself and honestly it was too quiet in April.