Nudibranchs are a group of soft-bodied, marine gastropod molluscs which shed their shells after their larval stage. They are noted for their often extraordinary colors and striking forms, and they have been given colorful nicknames to match, such as “clown”, “marigold”, “splendid”, “dancer”, and “dragon”. Currently, about 3,000 valid species of nudibranchs are known.

The word “nudibranch” comes from the Latin nudus.

I have not tried to identify this species, which was filmed in the Philippines.