This is a support for a raft you can make from two plastic water bottles. It was designed to fit the Costco Kirkland Signature water bottles and has a short mast for a straw. A sail can be taped to the straw and also secured to the mast at the bottom to keep it from spinning.
For some reason the mast part warped when I printed it, but hopefully that was just an anomaly for my print.
I printed this laying on its side and using supports from the build plate. The mast still warped but not enough to ruin it.