Sashimi Jellyfish

Level 11 · Red Belt

Strategy:

Finned & Sashimi Fish

Overview

Sashimi Jellyfish is the four-row variant of sashimi fish. A Jellyfish pattern with missing base cells, compensated by fins, allows restricted eliminations.

How It Works

Find an almost-Jellyfish with missing base candidates.
Fin cells in the same block compensate for the gaps.
Eliminate the candidate from cells seeing both the fin block and the cover columns.

Example

Starting position

Look for Sashimi Jellyfish.

Sudoku grid showing the initial puzzle state for Look for Sashimi Jellyfish.

1

Columns 1, 2, 6 and 8 form a Jellyfish on 7

Base columns 1, 2, 6 and 8 form a Jellyfish for digit 7 in cover rows 1, 4, 5 and 8.

Sudoku grid illustrating step 1: Columns 1, 2, 6 and 8 form a Jellyfish on 7 — Base columns 1, 2, 6 and 8 form a Jellyfish for digit 7 in cover rows 1, 4, 5 and 8.

2

r2c1 is already filled

r2c1 is already filled with 8.

Sudoku grid illustrating step 2: r2c1 is already filled — r2c1 is already filled with 8.

3

r3c1 is already filled

r3c1 is already filled with 9.

Sudoku grid illustrating step 3: r3c1 is already filled — r3c1 is already filled with 9.

4

7 is blocked from r6c1 by the row

Digit 7 cannot go in r6c1 because r6c4 is already in this row. Remove the entry or choose a different digit.

Sudoku grid illustrating step 4: 7 is blocked from r6c1 by the row — Digit 7 cannot go in r6c1 because r6c4 is already in this row. Remove the entry or choose a different digit.

5

r7c1 is already filled

r7c1 is already filled with 4.

Sudoku grid illustrating step 5: r7c1 is already filled — r7c1 is already filled with 4.

6

r9c1 is already filled

r9c1 is already filled with 2.

Sudoku grid illustrating step 6: r9c1 is already filled — r9c1 is already filled with 2.

7

7 is blocked from r2c2 by the row

Digit 7 cannot go in r2c2 because r2c7 is already in this row. Remove the entry or choose a different digit.

Sudoku grid illustrating step 7: 7 is blocked from r2c2 by the row — Digit 7 cannot go in r2c2 because r2c7 is already in this row. Remove the entry or choose a different digit.

8

7 was already removed from r3c2

Digit 7 is not a current candidate in r3c2 because earlier solving steps already removed it.

Sudoku grid illustrating step 8: 7 was already removed from r3c2 — Digit 7 is not a current candidate in r3c2 because earlier solving steps already removed it.

9

r6c2 is already filled

r6c2 is already filled with 2.

Sudoku grid illustrating step 9: r6c2 is already filled — r6c2 is already filled with 2.

10

r7c2 is already filled

r7c2 is already filled with 8.

Sudoku grid illustrating step 10: r7c2 is already filled — r7c2 is already filled with 8.

11

r9c2 is already filled

r9c2 is already filled with 3.

Sudoku grid illustrating step 11: r9c2 is already filled — r9c2 is already filled with 3.

12

r2c6 is already filled

r2c6 is already filled with 3.

Sudoku grid illustrating step 12: r2c6 is already filled — r2c6 is already filled with 3.

13

r3c6 is already filled

r3c6 is already filled with 8.

Sudoku grid illustrating step 13: r3c6 is already filled — r3c6 is already filled with 8.

14

r6c6 is already filled

r6c6 is already filled with 9.

Sudoku grid illustrating step 14: r6c6 is already filled — r6c6 is already filled with 9.

15

7 is blocked from r7c6 by the row

Digit 7 cannot go in r7c6 because r7c3 is already in this row. Remove the entry or choose a different digit.

Sudoku grid illustrating step 15: 7 is blocked from r7c6 by the row — Digit 7 cannot go in r7c6 because r7c3 is already in this row. Remove the entry or choose a different digit.

16

r2c8 is already filled

r2c8 is already filled with 1.

Sudoku grid illustrating step 16: r2c8 is already filled — r2c8 is already filled with 1.

17

r3c8 is already filled

r3c8 is already filled with 2.

Sudoku grid illustrating step 17: r3c8 is already filled — r3c8 is already filled with 2.

18

7 is blocked from r6c8 by the row

Digit 7 cannot go in r6c8 because r6c4 is already in this row. Remove the entry or choose a different digit.

Sudoku grid illustrating step 18: 7 is blocked from r6c8 by the row — Digit 7 cannot go in r6c8 because r6c4 is already in this row. Remove the entry or choose a different digit.

19

r7c8 is already filled

r7c8 is already filled with 9.

Sudoku grid illustrating step 19: r7c8 is already filled — r7c8 is already filled with 9.

20

r9c8 is already filled

r9c8 is already filled with 4.

Sudoku grid illustrating step 20: r9c8 is already filled — r9c8 is already filled with 4.

21

The fin sits in box 8

One base column has extra candidates in box 8. That box is the fin, making this a Sashimi Jellyfish.

Sudoku grid illustrating step 21: The fin sits in box 8 — One base column has extra candidates in box 8. That box is the fin, making this a Sashimi Jellyfish.

22

Only box 8 can lose 7

Because of the fin, only cells in box 8 that also lie in rows 1, 4, 5 and 8 can lose digit 7.

Sudoku grid illustrating step 22: Only box 8 can lose 7 — Because of the fin, only cells in box 8 that also lie in rows 1, 4, 5 and 8 can lose digit 7.

23

Cells that see both fish and fin

These cells see both the fish structure and the fin, so they are removal targets: r8c5.

Sudoku grid illustrating step 23: Cells that see both fish and fin — These cells see both the fish structure and the fin, so they are removal targets: r8c5.

24

Remove 7 from the fin-affected cells

Remove 7 from these fin-affected cells: r8c5.

Sudoku grid illustrating step 24: Remove 7 from the fin-affected cells — Remove 7 from these fin-affected cells: r8c5.

25

Result

Result after applying the technique.

Sudoku grid showing the result after applying the technique

Tips & Patterns

Sashimi Jellyfish are extremely rare.
Master simpler fish patterns before attempting to find these.
Computer solvers handle these most reliably.