The drinking age in St. Thomas (U.S.V.I.) is 18. They are very liberal too.
I asked a bartender once if I could take my beer out onto the street. He said even drinking while driving is legal. Not that I'd recommend that but it shows how liberal they are.
According to bvivacations.com "There is no specific drinking age on the law books of the British Virgin Islands. According to the Attorney General's Office, the Liquor License Act (section 34) specifies that alcoholic beverages may not be served to anyone who "appears" to be under the age of 16 years."