Swordfish
Level: Advanced
A fish pattern that extends the X-Wing to three lines.
A Swordfish extends the X-Wing to three rows and three columns. It forms when, across three rows, the candidates for a specific number are confined to the same three columns.
Each row doesn't need to fill all three columns, but its candidates must not extend beyond them. Then you can eliminate that number from the rest of the three columns.
It's harder to spot than the X-Wing, but the principle is the same, and it broadens your understanding of fish-family techniques.