Logic Masters Deutschland e.V.

I'm quite pleased with this puzzle, but I will warn you that there's a pretty big difficulty spike part way through. It might only be a 4* puzzle, but I'm estimating 5* just in case. If you do get stuck and want a nudge, I do have some hints in spoilers below the puzzle. Thanks to everyone on the CTC and SST discords for help with testing. Hope you enjoy!

Rules:

Nurikabe: Shade some cells such that all shaded cells form a single orthogonally connected region called the ocean, and all unshaded cells form islands. No 2x2 region may consist entirely of ocean cells. Each orthogonally connected set of island cells will contain exactly one Surveyor Arrow.

Surveyor Arrows: A double arrow pointing along a cell's edge is a Surveyor arrow. It will be placed on an island, and the edge it points along will always be a shore (i.e. the cell on the other side will be ocean). The number placed in that cell will be equal to the number of cells that belong to that island. The number will also count how many cell lengths that shore line extends from one end to the other while traveling in a straight line. The measured shore line may belong to several islands. The count only stops when continuing would mean passing between two ocean cells, two land cells, or off the edge of the grid.

Click the puzzle to play!

Highlight the text below to reveal some increasingly specific hints if you get stuck, or feel free to reach out to me on the CTC discord if you need a more case-specific nudge. Hope you enjoy!

The back half of the puzzle centers around ocean connectivity.

Can ocean ever travel through a shore line?

How do some of the potential island + shoreline combinations affect the oceans globally?