I believe this is officially called the Fort Casey Underwater State Park. Many think this is the best shore dive in the Northwest (excluding the San Juan Islands of course). The jetty is over 200 feet long and consists of very large boulders. To say the current can be challenging is an understatement. Depths are about 60 feet maximum at the end of the jetty. Wind chop can be severe. I would select a day when there isn't much tidal exchange and dive at slack. Because of the high current here it is a great place to dive. Vis. can be quite good and the marine life is plentiful and varied. The jetty rocks create lots of neat caves to look into. I wrote that we saw at least one wolf eel, lots of china rockfish and large perch in the shallower areas. I would recommend a "tour" going all around the Jetty. Lots to do shore side (hikes, gift shops, beaches) on the island and at Fort Casey for non-divers. As for directions: From the Seattle side take the Mukilteo Ferry and drive north on Whidbey Island about 21 miles on St. Hwy. 525. Then take Hwy. 20 about 3 miles to Keystone. The Jetty is adjacent to (and south of) the Keystone-Port Townsend ferry dock. Of course from Port Townsend you take the ferry to Keystone and you are like there already. Bring a U/W light and ferry fare to get home, driving around over the Deception Pass Bridge is a long, but scenic way to drive back to Seattle.