FWIW, Seattle is not near the Pacific. THe ocean is a several hour drive.
Whidbey Island is nice and is about 1.5 hours north. A ferry is required to get on at the south end which runs every 30 minutes but could be a 2 hour wait on summer Friday afternoons.
Hood Canal is also pretty.
Also know unless you are a polar bear or kid, the water is NEVER warm enough to swim in.