Known locally as 'The Grotto', this spectacular 'blow-hole' is situated in the West Quarter of Inishbofin. This one is unusual because not only can you walk down into it, the sun also shines directly to the bottom, illuminating the gapping hole for about an hour each day. Above you can see the eroded passage out to the sea, the blue area in the mid-distance is light entering from a second 'blow-hole', a short distance away to the North. While taking this shot, a large seal came up the passage to the rock in the distance, stuck it's head up, then disappeared. A really beautiful place, shot in perfect weather and light. I'm guessing it would not have the same visual impact on a dull day.
Photo: Shot in bright sunlight. 10-20mm wide-angle lens @ 16mm. This is a 3 frame, in-camera multiple exposure. ISO 100. 30 seconds (x3 = 90 seconds). f/13. A B+W 10 stop filter was used to achieve the slow shutter speed.
On the subject of 'grottos', here's one taken of an old wreck on the beach.