There's also another unusual way - the Caisson lock.
Its design is TERRIFYING.
The boat is floated into a tube that get sealed at both ends and then (in the dark..) that tube is winched down into a completely flooded chamber until it (hopefully) lines up with the egress port at the bottom. The tube with the boat in is unsealed and the boat floats out.
Its design is TERRIFYING.
The boat is floated into a tube that get sealed at both ends and then (in the dark..) that tube is winched down into a completely flooded chamber until it (hopefully) lines up with the egress port at the bottom. The tube with the boat in is unsealed and the boat floats out.
https://en.wikipedia.org/wiki/Caisson_lock