I looked here to see if I could find it, but it isn't listed:
Maybe it's still Navy or service-affiliated, but not run bt MWR? I don't know. if it is and you have a way to use it - current active duty/reservist or retired military - they seem to have very good rates for slips. The one's up here (Everett and Whidbey Island) were the cheapest I've found by far.