Since the tension is not changed, the wave speed is not changed. So, a decrease in wavelength means an increase in frequency. Without additional information, we cannot predict which will float. Whether or not an object floats is a question of how its density compares with the density of water, and not the weight of the object. Give an example of each.
Convection occurs when a mobile fluid moves between objects at different temperatures.
Turning the heater on in your car is an example of convection. Radiation is the transfer of heat by means of electromagnetic radiation. An example of this is the energy we receive from the sun. Suppose we place an ice cube in a pan, and place it on the stove. Soon the ice melts into liquid water, and after a while boils to form steam.