ID needed please.

[Seasidedeb]

Flashlight duty last night and found an unusual creature. Its about pinky width and length. Grey blue bod with red frills/edges on both sides of the body. I saw it and watched it for a while. It moved very slowly. The red edges of this creature are the sides of its body not a bristle worm bedside it. I have bristle worms and this doesn't look anything like them. Any help will be greatly appreciated. ID, friend or foe? I know the other 2 circled are sponges. Just need the ID on the other critter. Thank you.

 

[Coralreefer1]

Possibly a Peanut worm, Sand Worm or Madusa Worm.

 

[Seasidedeb]

Thank you!