Never ever heard of white sea or white knight

Tenuous at best, rough sea and chess..but weak.

wrong night/knight no?

White Sea is located in north west Russia, where they get "White Nights" (It stays light for most of the night during midsummer)

Really good grid. Smolenkoy has got it spot on, no further explanations needed.

Sometimes we should question our own knowledge when something doesn't appear to make sense, rather than the grid.

Perfectly reasonable grid. Thanks very much.

White night AKA "nuit blanche" is a sleepless night.
Perfect grid

Problem: everything that's "white" here can also be "black." The Black Sea is much better known than the White Sea, a black lie is one that's intentionally harmful, a Black Russian is also a cocktail, and "white night" only works as a colloquialism to begin with because it contrasts with "black night," which night usually is.

Nice grid! A "black lie" is at best a rare neologism and "black night" is not a thing at all. So, no problem.

It is white Knight, not night. The connection doesn’t work with out the k.