Hello
briangibbins, if you have Go Fishing playing friends you can ask your friends to send you the items missing on your Sea collection as a gift,
Updated on May 2020 by Icebear
or if you would like to try catching items yourself, players reported catching Sea Collection items at these locations:
(listing only reported locations, it may be possible to catch Sea Collection items at other locations also)
Black Sea 
GBR
Hawaii
