Do similar things to you, except we have never done the submarine.
We like to visit churches and forts. One reason we like San Juan and the Mexican Riviera.
We also like to eat ashore, try out the local food. Mexico has some great places where you can sit on the beach and have a great meal.
We are also ultimate tourists, if there is something to see, we usually see it. We have a San Juan-San Diego cruise set for April and we are really searching the net for trips. Found some great excursions in Costa Rica, canopy walking through the top of the rain forest.