Deep One Fossil

This artifact was found in a chest Obed Marsh had when he was sailing in the south seas  on a second trip to the so called 'islanders"
Obed Journal reads " These  Islanders seem to be doing great all the fish they can eat  trade is good i can make a real catch here...the chief asked too see me today  grabbed a bag of trinkets  , you never know.... this  cant be real i have  never seen this before  they called it a ....Deep One what are they.....