My wife & I have been to a number of Caribbean islands (Bonaire, Grand Cayman, Turks, St Martin and others) Our last two trips were to Bonaire & Turks in early March. On both islands we found the surf so rough getting in from shore at most sites was not possible because neither of us are that steady on our feet anymore.. So we would like to find an island with good off the shore snorkeling in calm waters. Recommendations please.

In the winter, and March is still winter, storms in the north Atlantic can make for rough water on any island. Typically the south facing beaches are not affected as much, but no promises! In the USVI, people can be surfing on the north shore and snorkeling calmly on the south. ;-)

Look into West Bay Beach in Roatan. After enjoying places like Grand Cayman, Belize, St John, Akumal MX,.....my next trip is going to be Roatan. The reef is 50 yards off the beach...and looks incredible. Check it out...

After 20+ islands---some good walk in snorkeling was enjoyed on St. John (Caneel Bay resort and driving around to other beaches) and also Secret Harbour on St. Thomas. We are not big fans of St. Thomas, but our stay at Secret Harbour with the underwater wonderland was quite nice.

http://www.secretharbourvi.com/

We used to "chase" good snorkeling from island to island. You've been to Grand Cayman, some nice spots there. I must say, the above was the best for us.

Oooops! Early March? I just saw that. All that good snorkeling I posted above was later than that.
Early March, maybe Barbados, we had some great turtle chasing at that time of year.