The energy they are reffering to is heat . When you swim in cold water the heat of your body is transffered to the water becasue i guess it s because it wants to reach and enqilibrium within the systems.Nature in general doesn t like gradients.And also in water we loose more heat compared to air of the same temperature i guess this happens because water compared to air is a liquid it has (greater density, it s directly in contact with our body)
Find the density of the plastic. if the density is less than that of water, it's going to float. If it's more than the density of water, then it's going to sink.
