A Finned Fish is akin to an almost linked set, in that it is one candidate (or tertiary unit) short of being a fish. Either the fin is true or the fish is true, not both. This exemplifies that there is a weak connection between the fin and the fish. The following is a list of the solving techniques currently used in Sudoku Snake that utilize finned fish.
Finned fish of higher magnitude may exist, namely for mutant squirmbags, whales and leviathans. However, due to the rarity of these occurences and the high amount of processor time required to identify them, they are not currently used by Sudoku Snake.