Windjammer cruises are built around beaches -- and seeking out sun and snorkeling are most peoples' primary concerns. Only a few excursions in the traditional sense are offered through Sagitta. For example, on Nevis, passengers can sign up for a taxi tour of the island or take a picnic lunch to Shoal Bay on Anguilla. For the most part, it's up to you to create your own fun.
On Sagitta, a 16-person dinghy ferries you to shore for a dry or wet landing. The latter can be a bit dicey, even for the fit: an unexpected surge off Anse Colombaire, a marine preserve on the remote side of St. Barts, almost sent us spilling into the surf. That being said, the staff go out of their way to warn the less mobile if conditions look dicey. It's nice to be treated like a grownup.
Evenings on the ship can be quiet or rowdy, depending on who's onboard (and how much rum is being consumed). On our trip, people spent their time reading, socializing or playing dominos, and a few hardy folks took a night swim. One night, the ship organized a beach barbeque at the Shiggidy Shack in St. Kitts' Frigate Bay. If the ship is docking overnight in a small bay, the crew will send tenders as late as necessary if passengers want to check out nearby beach bars or nightlife.