One should never confuse a sea cucumber, a weiner, and a slug! They all have very different functions, none of which I will describe.
Yes, another worthless and pointless tangent from me.
Blessed are the namako, known as sea cucumbers to you gaijin. Out in Kaneohe Bay on Oahu where I did Japanese introductory dives (Jap dunking), there were all sorts of these wonderous creatures.
You had your big gnarly ones that were fun to wave at the Japanese. They would make some really strange noises underwater, especially when you had a nice big thick fat 2' cuke.
My personal favorites were the smaller black and pink smooth critters - about a foot long and a couple of inches thick.
On one day, when we had 12 females in the group, I grabbed one and stuck under the bottom seam of my shortie wetsuit. While my briefer, Susumu, was starting his spiel, I climbed up on the barge behind him and walked right in front of the gals - they were in the water at about the level of the namako which was hanging below my knee.
Not one of them would look up, and I started telling Susumu that his customers were not paying attention. He was getting really bent out of shape at them for not paying attention and I was needling him - plus he had a hangover.
The DM's watching this with a namako hanging out of my wetsuit leg were laughing, so I told Susumu that they were laughing at him and his inability to properly brief our clients. It was great watching him get ready to go into spontaneous human cumbustion. Then I stood back a little and squared off with him so he could have a good look. He started laughing, and this of course confused the 12 Japanese gals waiting to go dive.
When I pulled the namako out, they all make weird noises. Then the screaming began when I jumped down waving it.
Dogs are ok, but namakos are an instructor's best friend.