Yes, RIPTIDES is a Scrabble word!

Letter values in Scrabble US: R 1, I 1, P 3, T 1, I 1, D 2, E 1, S 1.

Is it a valid word?

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

a stretch of turbulent water in a river or the sea caused by one current flowing into or across another current
a strong surface current flowing outwards from a shore

Also: tide rip, rip current.