To reproduce:

1. place farmland/grass path next to a solid block (like dirt)
2. place a boat on the farmland/grass path. Be sure that it is not on the solid block.
3. Enter the boat.
4. Attempt to go on the solid block

       You can't

This might be an intentional gamefeature, but it is very ennoying that boats can't travel that one pixel up. Also, players and other entitys can get up them without jumping, so why boats can't?