Cover art for Patrick O’Brian’s Aubrey-Maturin series book. Sunset in the Indian Ocean, viewed from the upper masts of HMS Otter. The Otter, a ship-sloop, was a relatively small vessel with 18 guns. Beyond her are the larger frigates Boadicea, Sirius, and Nereide. All the ships are busy shortening sail and taking in their topgallants – a common precaution at nightfall if squalls were expected.