Alki Beach is Seattle's closest thing to a California beach. There is kayaking, beach volleyball courts, fire pits, and so much more!
There is parking for about a mile along Alki Ave. SW, however it quickly fills up quickly so get there early. The beach is about a mile long and since there is little parking there is a good chance you will need to walk a fair distance.
There are many things to do at this beach. There are kayak, paddle-board, rollerblade, and bike rentals all along the beach. Six fire-pits are also sporadically placed along the beach and are able to be used at a first come first serve basis.
Overall, if you are in Seattle on a nice day, this is a must see location.