Here are my thoughts on Vieques:
Vieques is the anti Key West. There is no "big town", no major grocery stores, no partying or clubs, and only okay restaurants. Vieques isn't the right trip for everyone. Its not a great place for kids and people who want a lot to do at night...go to St Thomas if you want that. For me and my girlfriend, it was perfect. We both work in NYC and found the perfect place to escape.
Vieques is great. You can be on a great beach and not see people for miles. It was like that all week, you see people, but everyone sticks to themselves.
If you want a place to snorkel, the snorkeling is mas or menos. The sea can be rough, reducing visibility. Also, the best reefs are in the restricted area. Make friends with a local and they will take you there.
-> Hidden Path at Navio that leads to an underwater cave.
-> Surfing in Navio.
-> Paddleboarding trip. Great great time, a blast and lots of laughs were had. I recommend this trip to anyone. I loved it.
-> Getting a drink spiked at the W hotel.
-> Not being able to get gas because the ferry hasn't arrived yet
-> Biobay tour. Very boring. Zzzz.
-> Not finding a place to eat because the restaurants close very early.
Come to Vieques to relax and unwiind. If you like unspoiled beaches, little tourists, and are willing to deal with the drawbacks, this is a great place. Beware of shootings in Esperanza though!