Yes, DROWNING is a Scrabble word!

Letter values in Scrabble US: D 2, R 1, O 1, W 4, N 1, I 1, N 1, G 2.

Is it a valid word?

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

cover completely or make imperceptible
get rid of as if by submerging
die from being submerged in water, getting water into the lungs, and asphyxiating
kill by submerging in water
be covered with or submerged in a liquid