Support your local bike shop: Ride the M/V Sally Fox to Vashon Island, or the new one coming to the West Seattle Route.
Or, contact these officials to ask for in-cabin bike racks like the old water taxis, or covered on-deck storage that excludes salt spray:
paul.brodeur@kingcounty.gov,
harold.taniguchi@kingcounty.gov,
Dow.Constantine@kingcounty.gov,
joe.mcdermott@kingcounty.gov
Here is what all four bike shops in West Seattle and White Center, and the closest to the water taxi terminal downtown, have to say: