Sitting towable for 1 or 2 teens

[elmonty]

I'm looking for a tube that will accommodate either 1 or two teens. My daughter, 15, prefers a sitting tube. I don't see many of those that will handle either 1 or 2 riders (except for large, expensive chariot-style ones).

Any suggestions?

If a towable on amaz, for example, says it handles 2 riders, can it also handle just one?