If Cyprus is here, which I think is only split by the UK, then the UK should also be here by virtue of its two Cyprus territories. And yea I don't see what metric you can use where Brunei shouldn't be in
There is a part of the Netherlands (with coast) which can only be reached by tunnel or through Belgium... Would be interesting to understand the view on that :-)
There are several other debatable countries, where inlets crosses borders, in addition to Brunei, Netherlands and Belgium, that already are mentioned: Ghana, Ivory Coast, Guinea, Guinea Bissau, Poland, Lithuania, Finland, Sweden, and maybe more.
This is all based on Google Maps so they may be inaccurate, but scrolling around the map I discovered:
-54.868566, -68.574618 where you could consideer Argentina and Chile to be interrupted if you count lago roca/errazuriz as coastal, but probably too marginal for this quiz just interesting.
A similar example here 4.363355, -7.531374 between Ivory Coast/Liberia
This one 6.927765, -11.504407 I think is actually quite convincing, I think the spit is Sierra Leonean and then it goes back to Liberia for a while. See also this this image on wiki where if you zoom in you can see the border goes through the spit. (Although if you look on satellite the spit connects back to Sierra Leone so maybe not)
Another: 10.989072, -14.918638 this one also seems quite likely to include Guinea/Guinea-Bissau
Also the Curonian Spit should include Lithuania and the Vistula Spit should include Poland
Brunei should absolutely be on this list. There's no way to continue along the coast of the island of Borneo from Bandar Seri Begawan to Temburong without going through Malaysia. Also, with the opening of the Pelješac Bridge in 2022, it's a bit debatable whether Croatia still belongs on the list.
Malaysia's coastline on the island of Borneo is broken up by the country of Brunei
-54.868566, -68.574618 where you could consideer Argentina and Chile to be interrupted if you count lago roca/errazuriz as coastal, but probably too marginal for this quiz just interesting.
A similar example here 4.363355, -7.531374 between Ivory Coast/Liberia
This one 6.927765, -11.504407 I think is actually quite convincing, I think the spit is Sierra Leonean and then it goes back to Liberia for a while. See also this this image on wiki where if you zoom in you can see the border goes through the spit. (Although if you look on satellite the spit connects back to Sierra Leone so maybe not)
Another: 10.989072, -14.918638 this one also seems quite likely to include Guinea/Guinea-Bissau
Also the Curonian Spit should include Lithuania and the Vistula Spit should include Poland