Landsickness is the opposite of
seasickness. It occurs once you have adjusted to the motion of a boat on the sea but then return to shore. The
vestibular system has adjusted to the constant motion of the sea, and it takes a few hours or days to readjust to being back on land. While seasickness can make you absolutely miserable, landsickness is generally limited to feeling unstable and wobbly, and often feeling like the ground is moving when you walk. This can be a falling hazard but it is otherwise fairly harmless.
Because landsickness sounds weird, some prefer to use the French term, Mal de Debarquement.