People do crazy things when under stress.
When I took arctic survival classes we had a mountain ranger from Maine give us a class on what to do when lost in the woods in the winter. The big thing was not panic and to make sure you walk in a straight line to where you think you need to go. Why?
Every person they find lost out in the snow does the same thing. First they panic, then they walk in circles (big circles so they do not know they are walking in circles). When dementia sets in they get frantic, sweat and take off their clothes. Then they freeze. Once they start freezing they lose it and most end up holding or hugging onto things like trees or rocks. He told us that many times they would find people who have little clothes on hugging trees and rocks and they would be so frozen you would literally have to pry them off of the tree.
He said these people are easy to find once you find their tracks. They then follow the tracks and find clothing items thrown off. Then they find the frozen bodies.
Hypothermia can also cause dementia. Those guys out there in the water probably lost their senses and had no clue what they were doing.
Remember: don't panic, stay calm.