By Jennifer Sinco Kelleher WAIANAE, Hawaii (AP) — Hawaiian petroglyphs dating back at least a half-millennium are visible on Oahu for the first time in years, thanks to seasonal ocean swells that peel away sand covering a panel of more than two dozen images of mostly human-looking stick figures. The petroglyphs are easy to spot during low tide when gentle waves ebb and flow over slippery, neon-green algae growing on a stretch of sandstone. This is the first time the entire panel of petroglyphs are visible since they were first spotted nine years ago by two guests staying at a bayside U.S. Army recreation center in Waianae, about an hour’s drive from Honolulu. Native Hawaiian cultural practitioner Glen Kila, who traces his lineage to the aboriginal families of this coastal…