Yes, UNSOUNDED is a Scrabble word!

Letter values in Scrabble US: U 1, N 1, S 1, O 1, U 1, N 1, D 2, E 1, D 2.

Is it a valid word?

UNSOUNDED is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

situated at or extending to great depth; too deep to have been sounded or plumbed
not made to sound

Not playable in Scrabble US: UNFATHOMED.