Anybody know what this is?

Don't show this to the Chinese

The highly toxic bootlace worm. It can grow up to 55m long

That is called pneumanatic singila symbiotic group. Basically you normally see them that size but sometimes they join eachother to make bigger ones. They are very rare to find. They have been known to cover at least 2-3 making them go psycho, hear things, and get controlled.