The Tres Reyes — Three Kings — are three small islands off Marinduque's southern coast named for the biblical Magi: Gaspar, Melchor, and Baltazar. They sit in clear water with coral reefs in reasonable condition, and the snorkelling around all three is among the best accessible reef diving in this part of the Philippines. The fish life is varied and the visibility is typically good outside monsoon season.
Gaspar is the largest and easiest to reach by banca from the town of Gasan; the crossing takes about 20 to 30 minutes. The beach on Gaspar is white sand with palm trees, and there are no permanent facilities — bring your own food, fresh water, and snorkelling gear. Melchor and Baltazar are smaller and less visited; arranging a banca to go to all three in a day is straightforward to organise in Gasan. The islands are best visited between November and May when the sea is calm.