Sea Serpent Grotto coffer key

[Ikon]

Anyone around that can confirm what drops the coffer key in sea serpent grotto ? I been soloing marsh,swamp,bog sahagin's and rock crabs for 4 days now and no key according to the list i got at treasurehunter those drop em . Am i just unlucky or not killing the right ones ?

[Kirk]

yup those are the right ones. I got mine in like 2 kills. Must be just luck... or lack of