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Basic Fish

Points.  All fish are single digit patterns. Basic fish like X-Wings and Swordfish have equal numbers of rows and columns. For an X-Wing, it is either 2 row truths and 2 column links or 2 column truths and 2 row links. A Swordfish is the same with 3 truths and 3 links, Jellyfish are 4, and Greatfish (Squirmbags) are 5. The patterns below examples of each fish. In real fish except X-Wings, it is not necessary to have all possible candidates. See  X-Wings, Swordfish, Jellyfish, and Greatfish.



X-Wing Pattern. The pattern to the right shows an X-Wing pattern made of two (red) truths in rows 3 and six. The candidates in the two rows see each other (linked green) in columns 3 and 6. The yellow candidates show all the locations where candidates can be eliminated. An X-Wing, link all basic fish, is rank 0.



Swordfish Pattern. This Swordfish pattern has 3 truths covered by three links as opposed to an X-Wing with 2 truths and 2 links. The logical reasoning is the same as the X-Wing, if all the candidates in 3 truths are contained in 3 links, then no other candidates in the links can be true, and can be removed.  

Swordfish Pattern, Minimal. This pattern shows a swordfish with the smallest possible number of candidates. If the center candidate is removed, the logic is still valid but it's called an X-Cycle. Only one example elimination is shown.

Jellyfish Pattern.  This Jellyfish is the size 4 member of the basic fish family.  Only one example elimination is shown.

Greatfish Pattern.  A Greatfish has a size of 5 but it is sometimes argued that they are not required as other, smaller patterns should exist along with the Greatfish. A Greatfish is more commonly referred to as a Squirmbag. Only one example elimination is shown.