What kind of worm is this?

Moving very quickly in less than 10 feet of water this "worm" was probing every crevice and crack as it moved. Stretching out to almost two feet long at times and about a half inch in width.

It is a ribbon worm (Phylum Nemertea). That one is probably Baseodiscus quinquelineatus (if it has 5 longitudinal lines).

Correct on sp ID. Nice pics!:-)

Jon - I only see 3 dorsal stripes. Does the number of dorsal stripes vary from 3 to 5?

Jon - I only see 3 dorsal stripes. Does the number of dorsal stripes vary from 3 to 5?

Trolling the site for first time in months...

I have to check why I didn't get notified on this response.

It has two ventral stripes.

Some of the pics I see that are labelled Baseodiscus quinquelineatus have 5 black dorsal lines on a white body. Sometimes the 2 outermost are close to the lateral edge but they're not ventral. What are they?