Shenick Island lies east of Skerries Harbour, separated from the mainland by a stretch of tidal sand. At low tide it is possible to walk across the sandflats to the island — a genuine tidal island experience in the Dublin commuter belt. The island is home to a Napoleonic-era Martello tower, harbour seals that haul out on the western shore, and nesting seabirds. The views back to the mainland and north along the coast are excellent.
The timing of the crossing matters: the sandflats expose completely at low tide and are impassable at high water, and the tide turns quickly. Check tide tables before setting out, and watch the water on the return. Most visits to the island take about an hour; you can walk the entire perimeter on a low-tide day. Sea kayaking tours from the harbour are an alternative way to visit without worrying about the tides.