Glowing dots in the ocean. What are they?

I was staying overnight at Samal Island (off of the island of Mindanao in the Philippines) and I walked out into the water. The water was very clear (I'm guessing since it is in the gulf of Davao) so I can see my feet below. I could see due to the full moon illuminating the darkness. As I took steps, there were small dots glowing. It reminded me of fireflies (lightning bugs), but they were kind of smaller and in the water. Well, they seemed to be embedded in the sand or gr. They gave off their flash/glow where I stepped, as if lighting up when disturbed. What made the lights?