Depends on the configuration and size of the boat. The size of the tube would come into play too, especially if it's a small boat.
Outboard or I/O would maybe make a difference. Again, depending on the boat.
Most just tie it somewhere up onto the back of the boat.
Some pontoons have tops and people tie them up there.
The main concern I would have is blocking the view of the operator.
If there's no safe way to tie it up, think about getting one of those 12v air pumps that not only inflate, but also deflate. They work pretty fast. Just deflate it when not using it.
