The pilot reported that he was intending to practice water landings in the amphibian float-equipped airplane; however, he neglected to raise the wheels after the initial takeoff from a paved runway. During approach for the first water landing at a large nearby pond, he did not notice that the wheels were still extended. The airplane subsequently nosed over when he attempted the water landing. He was not injured exiting the airplane. The airplane sustained substantial damage to the wings during the accident sequence. He reported no failures or malfunctions associated with the airplane prior to the accident. He added that he needs to be more dedicated to checklists in the future.