[dmos62]

I had this most vividly with kayaking. I'd slowly fall asleep rocking in the river, paying background-attention to keep balance in the kayak, even though I was in my bed or in a tent on shore. I'd then also dream about floating in the kayak.

[lupusreal]

Sounds like a variation of "sea legs". Standing on land after some time on a rocking ship very often produces an odd sensation of the land moving.

[dmos62]

I get that with a treadmill as well.