The best luck found us this cave at low tide, about 30min before sunset, my friend and I had simply been looking for interesting seascapes. This is a landmark that you can't see everyday. The tide and time of year determine if you can catch the sun shining into the grotto at sunset, and persistence (and a tide chart) are required unless you just like getting your feet wet. I went back several times over the course of two years, but I still haven't seen conditions this nice again.