The rooftop gun platform, partly built from granite, has grooves cut into the stone that channelled rainwater down into a storage tank in the basement, a practical detail that speaks to the realities of garrisoning troops on a tidal island with no reliable fresh water supply. Somewhere between military ruin and time capsule, the structure on Shenick's Island sits quietly at the north end of the island, neither restored nor entirely surrendered to the elements.

Martello towers are squat, thick-walled circular fortifications, a design adopted by the British across Ireland and along the English coast in the early nineteenth century as a defence against the threat of Napoleonic invasion. Construction of the Dublin-area towers began in 1804 under the supervision of Colonel Benjamin Fisher of the Royal Engineers, and by December 1805 all twelve towers north of Dublin were armed and complete, each mounting a single 24-pounder cannon. The Shenick's Island tower, recorded as Tower No. 10, was built from limestone masonry finished with a rough lime render. Its interior retains a domed ceiling typical of the form. By 1848 the tower was under the command of Ralph Allen Daniel, based at the Fair Street Barracks in Drogheda, and around twelve troops were stationed there as late as 1857. The military eventually lost interest; the tower was disarmed by 1874 and sold by the War Department in 1908.

Shenick's Island is accessible on foot at low tide from the Skerries shoreline, though the crossing requires attention to tide times and the ground underfoot can be unpredictable. Once on the island, the tower stands at the northern end, and to its south are the remains of a stone-built powder store and latrine, roofless but otherwise in reasonable condition. A stone well survives towards the southern part of the island. Worth noting for those who look closely: an Ordnance Survey marker sits on the cliff edge to the east, which is reportedly eroding rapidly, and a second marker lies on the ground between the tower and the latrine, apparently never installed. The island rewards slow exploration rather than a quick circuit.