Here are a few options for trips down to the various Batangas beach areas. It works best to book with them over the phone or by email instead of through the website. If you can do it through the website, that will be fine, but if you are finding it "booked" you should email them or call them.
Calatagan area:Aquaria water park.
Most of the resorts have day trip options. Emailing/calling the resort to schedule a day trip is necessary so they can be prepared for your visit as some of the day trip packages include food.
You are able to rent a boat to take you to a reef for snorkeling, though you may be able to snorkel right off the beach at most of these places. There are many other water activities to choose from and they can all usually be scheduled once you arrive. Relaxing on the beach or even getting a massage is also a good option.