Vieques is part of what are called the Spanish Virgin Islands. It is off the south-east coast of Puerto Rico and sits in-between the main island of Puerto Rico and the U.S. Virgin Islands (St Thomas, etc). Tourists and locals alike love going to Vieques both for its beaches as well as the island life. There you can find wild horses roaming! By boat, the snorkeling and beaches are amazing and there is also great fishing off the coast for the anglers.
Which hours/time frame?
You need a full day if you want to go to Vieques. A half day is not an option.
Which boats are best for this destination?
Any of the boats 30 feet and bigger can get you to Vieques.