This page has links to Federal, Washington State, and Seattle boating requirements, as well as a link to a Float Plan form from the US Coast Guard Auxiliary.
Don't get caught without the right gear. These are Federal minimum requirements - state and local laws and common sense may dictate carrying additional equipment.
Guide to Federally required minimum requirements, by size of boat. Contains basic info from above, but a bit easier to find requirements. Again, state and local laws and common sense may dictate carrying additional equipment.
To ensure your and others' safety on the water, get to know the state regulations for operating your boat
From the Seattle Harbor Patrol. Includes local speed regulations.
PDF form you can fill out before you go boating, and leave with a trusted friend or family member. Do NOT file with the Coast Guard.