When the first St Mary's lifeboat went into service in 1837, she was a pulling and sailing boat - oars on a heavy sea, sail when wind allowed, a hand-cranked baler when the swamp came over the gunwale. The station closed in 1855 and reopened in 1874 with a new boathouse built for £280 on the beach at Porth Cressa, a sandy bay just south of Hugh Town. By 1899 a more ambitious facility was needed: a stone boathouse and slipway at Carn Thomas, on the eastern side of the harbour, built at a cost of £1,500. In 1902 the local boatbuilder Robert Hicks extended the slipway by 40 feet so the lifeboat could launch at any state of the tide - a critical capability when distress calls did not wait for high water. The first motor lifeboat finally arrived in 1919, after the boathouse had been adapted in 1914 to receive her.

St Mary's lifeboatmen have earned twenty-six RNLI medals for bravery - one gold, nine silver, sixteen bronze. The gold is the highest peacetime honour the RNLI awards. These medals are not casually given. They mark services where crews put themselves between death and someone else, usually in conditions where remaining onshore would have been entirely understandable. The Scilly Isles sit at the southwestern corner of the British approaches: every ship inbound from the Atlantic, every fishing boat working the southwest grounds, every yacht miscalculating a Bay of Biscay crossing comes within reach of these waters. When something goes wrong out there, the St Mary's boat is often the nearest help available, with the next-closest stations at Sennen Cove on the mainland and St Agnes on the next island over.

Since the arrival of the Robert Edgar in 1981, the St Mary's lifeboat has been kept at her mooring in the harbour rather than hauled into the boathouse between calls. Modern Severn and Tamar class boats are too large and too heavy for the old slipway, and a moored boat can be at sea minutes faster anyway. The current boat is the RNLB Whiteheads - call number ON 1229 - a 17-metre Severn class capable of 25 knots and a 250 nautical mile range. She launches from St Mary's Harbour, the same patch of water where every Scillonian arriving from Penzance ties up alongside a fishing boat or two. When her engines fire and she heads for the open sea, the harbour goes quiet for a moment. Everyone watching knows where she is going, and that the people aboard her chose this.

The most recent bravery medals at St Mary's were awarded for a service carried out on 29 October 2003. A man on a yacht had been seriously injured. Coxswain Andrew Howells, crew members Mark Bromham and Philip Roberts, and the rest of the lifeboat crew brought him off. The RNLI does not award medals lightly, and the citation - bronze for all three - records that the conditions and risks involved went beyond ordinary service. Their names are now on the same honours board as crews who pulled survivors from the 1983 British Airways helicopter crash in the sea off St Mary's, from countless fishing vessels lost in winter gales, from yachts caught out by the Western approaches. The medals are receipts. The work continues.