What is this?

[loweryphil]

 

[slipknotgrrl83]

No idea...hard to tell with the pic. Is it attached to rock?

 

[Nick92515]

Could be anything, need better pics

 

[loweryphil]

Small snail thing on glass dunno if its bad or not

 

[Sm51498]

Nudibranch or elysia, hard to tell from the pic. I think nudibranch though.

Odds are it will die, nudibranchs are very specific in diet.

 

[loweryphil]

Ok heres a better picture

 

[loweryphil]

 

[Coastie Reefer]

looks like a nassarius snail

 

[Lionfish Lair]

Look up columbellids and see if looks the similar.

 

[Sm51498]

Crazy, couldn't even see the shell in your first pic. I would be concerned it is a predator there are several good guides out there on whelk identification.