Mystery trophy?

Err...I just got this weird trophy called "Sea Legs". (I actually didn't notice it before...I'm not even sure if I got it today.)

AND I ALSO GOT INCREDIBLE RIGGER! :D To complete my incredible collection, I need 3 more: Alchemistry, Distilling and Shipwrightery.

T_T

Don't worry, I'll get it SOMEDAY!