It will be crowded for sure! If you are good with a predawn arrival at 4am you will likely beat the rush and get a spot to park with little trouble. If you arrive at 5:30ish you will likely be in a long launch line and maybe have to park on the street outside the lot. The one good thing is that all of area 10 will be open so the other launches like Shilshole will spread out the crowds a bit.
I fished it last Friday for the Elliot Bay opener and beat the crowd thankfully. It was crazy how many boats were on Elliot Bay for a Friday, most I've ever seen and I've been fishing it a long time.
Better to get there early and just hang out on the water for bit before fishing, rigging up, eating breakfast, whatever.
