This is my African Queen, berthed behind a barge on the Thames in east London. That's not her real name, of course. She's the Royal Iris, once a familiar sight on the Mersey and now ending her days on a strange stretch of water. But the sight could not be more redolent of a lifetime of riverine slog if Humphrey Bogart himself was at the wheel beneath a soot-blackened stack.

Two-hundred miles to the north, the ferry across the Mersey, the Iris's old incarnation, has been reinvented as a showboat, a tourist attraction. "The most famous ferry in the world" cruises up-river and back again in stately arcs, befitting her swanky new status. A tape-loop encourages passengers to disembark at Seacombe and Woodside, for the "Pirate's Paradise" and fine dining respectively.

Well, full marks for effort. A trip around the bay complements Liverpool's other crowd-pleasers, the Tate Gallery and the rest of the Albert Dock. But the ferry was once a workhorse and can't shrug off her past so easily. In the 17th century, Daniel Defoe was shipwrecked aboard her before being carried ashore by "some honest Lancashire clown". Dickens liked the ferry "for the air". Her bread and butter was the most direct passage between Liverpool and the Wirral peninsula, as the gull flies. In the summer of 1965, she carried more than two million people from Liverpool to New Brighton, Merseyside's answer to the Sussex Riviera. But foreign package holidays did for the Costa del Scouse. In 1973, only 200,000 made the crossing, and the service was eventually discontinued. The revenants of the brief sunlit boom crowd the Wallasey shore, just as the ghosts of other industries - shipbuilding, the docks - do elsewhere in the estuary. The tape-recording acknowledges the former fairground where a great tower once stood, taller than its upstart pretender along the coast at Blackpool. There's also a namecheck for a building known as "the Stereo" - really a ventilation shaft for the Birkenhead road tunnel - and the Guinea Gap baths, which were filled with water drawn straight from the Mersey. On the day they opened, my great uncle Harry, the local councillor, was the first to take a dip. I think he was thrown in.

The shipboard commentary naturally steers clear of the sinking of the tugboat Applegarth in the Sixties with the loss of all hands. Another uncle, Leslie, was the skipper. He and his crew were never entered in the book of remembrance at Our Lady & St Nicholas, the sailors' church, perhaps because an accident inquiry and the coroner's report failed to dispel scurrilous rumours on the waterfront that my relative had been to blame. But it's been 40 years. I wrote to the church authorities. I went back to Liverpool for the first time after sending my letter. In the porch of St Nick's, the homeless men parted obligingly. In the book, there was no reference to Leslie under his own name. But I was pleased to find it under "A": "In memory of the men of the Applegarth."