Several here have mentioned the Cuan Law. My wife and I and two friends went on a 6-day on the Cuan in February. My wife was the only non-diver on the boat, but she had a blast. Scenery, weather, food, crew and everything else were awesome. In fact, on one dive where all of us were diving a wreck, one of the DMs who stayed on board got my wife to take a test dive - she loved it so much that she now has her own C card and we're going to Costa Rica for a week next month.