Improvised Boat Project

Mechanical engineers should know better.
The elastic tube has very little overpressure so cannot retain its shape when partly submerged. The part under water contracts, the part above expands until a nail, splinter or thorn in the raft above will end the fun for the occupants. For the spectators it starts there.

Only in a tire and around a rim the tube can survive, but then there is hardly any buoyancy left. Bad idea....

 

Here u go ... just have a spare motor and fuel tank in your garage and use your dinning table .....