There IS accessibility, but only if you can use a bump step transfer in both directions. A bump step transfer is basically bumping one's buttocks up and down a stair like construction.
There is no boat that can accommodate a wheelchair. There's a whole history there, tied to the use of ride systems and what actually needs to be modified regarding accommodations. It affects a bunch of Disney rides, including Space Ranger Spin (which uses the original tracks from "to fly," the doom buggies, and more.