Prince Eric's statue was a present given to him on his 18th birthday. The statue was commissioned by Grimsby, who had hoped to be able to give it as a wedding present rather than a birthday present. However, Eric is shown to be a bit less than pleased. Later, a storm sinks the ship, resulting in the statue falling to the seafloor. It is later found by Flounder who gives it to Ariel, as she had fallen in love with the prince. When King Triton discovers that Ariel not only rescued a human, but has fallen in love with him, Triton angrily destroys it with his trident.
The same happens in Kingdom Hearts II.