Glassy blue suggests bright blue eyes, and you can imagine the sea washing up azurely.
‘The islands are spread over a vast warm sea, but the air makes them stepping-stones. Bottled within them, behind their glassy-blue shores, you will find an eccentric brew preserved.’
Source: Laurie Lee, I Can’t Stay Long (Harmondsworth: Penguin, 1977 ((1975)), p. 196