The pilot reported that, during takeoff from a beach, the airplane lifted off and reached about 10 ft above ground level, but he then "felt something holding [the airplane] down." He lowered the nose to build up airspeed and attempted to climb again, but the airplane was unable to climb due to a downdraft. The pilot was unable to abort the takeoff due to increased airspeed and reduced landing area. The airplane was heading toward a 50- to 60-ft-tall bank, so he decided to "pull up" and attempt to fly over it. The airplane continued for about 3/4 mile, aerodynamically stalled, and then the empennage impacted terrain. The airplane continued about 30 ft, struck a big clump of dirt, and nosed over. The airplane sustained substantial damage to the left wing. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation. The pilot reported that the wind was variable at 27 knots, gusting to 36 knots.