HoDoKu Finned Mutant Swordfish

Finned Mutant Swordfish: box 3, row 4, col C and row 1, row 9, col G on 2 (A9-2)

All the possible positions of the value 2 in three base box/row/col are in the same three cover row/col. The number of box/row/cols matches the number of row/cols, and each box/row/col must contain the value 2; so each row/col will have a 2 in one of the intersecting cells.

Hence the other possible positions of the value 2 that are in the row/col but not in one of the box/row/col may be removed.

Therefore we can remove A9-2.

Explanation

Mutant Fish use all three types of regions (box, row, and col) as both base AND cover regions. Note that MOST mutant eliminations will have already been found by simpler Fish types, so they never show-up, and with all three region types in play the number of combinations of regions EXPLODES, so searching them is MUCH slower; but we still find a few, so we do it anyway; mainly just because it was there.

Note that HoDoKu incorrectly reports Mutants as Frankens. I'm not going to fix it, because the code is MENTAL.