Protected Schooling

Question

_{This is part 26 of the puzzle series Around the World in Many Days. Each part is solvable on its own.}

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Dear Puzzling,

This is a Shakashaka puzzle. Mark some cells half-shaded along a diagonal (one half white, one half black), so that every remaining white area is in the shape of a rectangle. Some cells have numbers in them; the number indicates how many filled-in (half-shaded) cells the numbered cell shares an edge with. In the crossword, the wordplay part of every clue gives one letter too many. These extra letters must be omitted when entering the answers into the grid.

Today I have explored the coral reefs around a tropical paradise island and truly appreciated the variety of marine life that can flourish in such an environment when humans take the appropriate steps to protect it. I have seen sea turtles, dolphins, manta rays and hammerhead sharks schooling in the pristine waters. Can you guess where I am?

Love, Gladys.

Shakashaka on Penpa+
Crossword on Penpa+

Across
3. Mr Mourinho who coaches an average fellow? (3)
7. Piece of rope seen twisted to bind couple of kangaroos (5)
8. Unequivocal plus sides (3)
9. Spanish banker's brother apprehended by backers of Portuguese police (4)
10. Coco regularly destroys trends (6)
13. Engineer damns worst fighter (9)
16. Requiring knowledge which is difficult to obtain and can wear off (6)
18. Roald who wrote about Yankee woman (4)
20. Leaders of Islamic republic intentionally aiding paramilitary organisation (3, abbr.)
21. Lift off – it's hot (5)
22. Echoes surrounding copper's signal to act (3)

Down
1. What's involved in foundin' a telephone company? (5)
2. Adopt either side in bitter fight (6)
3. Canadian player belonging to Skopje ethnicity (3)
4. Mountain that's always in the direction of Spokane when looking from Seattle (7)
5. Interrogate Marquis Zhao's prisoners (4)
6. Osiris managed to remove head of Ra, an important figure in Egyptian mythology (4)
11. Working after Iron Age (3)
12. Intense French shenanigans (7)
13. How to address a knight's assistant (3)
14. Computer-programming woman soldier seen near Australia being leisurely (6)
15. Perhaps alt right to go to capital once (5)
16. A beast of burden is showing Italy, Germany and others (4)
17. Scottish family on medium-sized steamer? (4)
19. That man supports Anglican Church activist (3)

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Gladys will return in Hiking Circuits.

Answer 1

Part 1: Shakashaka

Basic deductions:

On the right side,

the 1 clue cannot be empty both above and to the right; this would mean the cell ↗ward of it would have a triangle that cannot complete a rectangle.

Next, consider how the center will resolve.

We can't put a ◣ in the lower left corner; that would create a 2×2 diamond, and trap the cells to its right. So that cell must be empty.

This creates a 'chain reaction' which starts to propagate around the grid:

Now, in the lower right,

we have to extend the bottom rectangle fully, and squeeze another ⋄ in the corner.

And the puzzle is complete! Final grid:

Part 2: Crossword

The finished grid:

Clue explanations:

Part 3: Putting them together

The extra letters in the wordplay of the cryptic clues

spell out "SELECT WHITE AREAS OF SIZE ONE".

Doing this...


gives ISLA DEL COCO, also known as Cocos Island, a national park of Costa Rica.