Why do floating plants have waxy coating on their leaves?

so that the leaves wouldnt be all soaked up with the water, and sink as they have short stems (their pretty small as well compared to partially submerged plants) they will eventually die due to insufficient amount of food (taller plants block the sunlight) and also will have too much water. they will die also due to overcrowding, this also occurs on land plants because the parent plant will get more sunlight and the young plants have to compete with them. in the water, too much floating or partially submerged plants will start to block eachother from the sunlight, depending on which grows more. they also completely block sunlight from the submerged plants down there.