Hardy Fendel has heard any number of theories about what caused a Rhine River tourist ship to crash on the rocks below the Lorelei cliff three weeks ago.
Along this pretty but perilous stretch of the Rhine, the accident -- which injured 41 people, 3 seriously -- has dominated the dockside chatter among river pilots like Mr. Fendel.
The police believe the ship ran aground, shearing off its propellers and sending it into an uncontrollable spin through the currents. The Rhine, they noted, was at its lowest levels in recorded history after a severe drought. Some locals whisper that the boat's skipper was nodding off at the wheel.
For Mr. Fendel, a wind-worn man who has piloted tugboats on the Rhine for 45 of his 65 years, there is no mystery: the ship, and its romance-hungry passengers, fell victim to the siren's song.
''It was Lorelei,'' Mr. Fendel said of the maiden who, legend has it, lures sailors to their doom with her sweet tones.
As he putt-putts slowly past the rocks where the boat crashed, squinting into the morning mist for other boats, Mr. Fendel remarks that it could have happened to anyone. ''When I reach the Lorelei cliff,'' he said, ''I sometimes take out my binoculars to search for her beautiful eyes.''
The Rhine is often called Europe's watery main street. This year, it has become a dangerous main drag.
In January the river burst its banks after heavy rains, leaving the towns here under three feet of muddy water. In September, after an arid summer, it all but dried up, enticing teenagers to wade across while turning one of Europe's most critical shipping routes into a gantlet.
Even now, after some rain, the Rhine remains hazardously low in places. Rocks jut out of the water, offering flocks of cormorants an unaccustomed perching place. Sandbars cut unsightly swaths through the currents, forcing ships to navigate a serpentine path around them.
For the officials who watch over the Rhine, it is debatable whether a flood or a drought is the bigger headache.
''When the water is too high, we halt all the river traffic,'' said Petra Schneider, the deputy head of the Rhine Water and Shipping Authority in Bingen. ''When the water is low, we don't stop the traffic. It's up to the pilots to judge the risk of whether they should use the river.''
The rule of thumb is that a boat can sail if there is merely the width of the span of a person's hand between its keel and the riverbed. That is cutting it pretty close, Ms. Schneider concedes, as she lays a delicate hand on her desk to demonstrate. It is also a bit imprecise, given the wide range of hands.
For Heinz Engelhart, the skipper of a tourist ship, the hand-span rule is charming but outmoded. He knows exactly how much margin he needs (just under a foot), and scrutinizes daily water measurements to make sure he will not scrape the bottom. As he pilots his ship, the Ehrenfels, downstream, Mr. Engelhart hugs the middle of the channel, passing within a few feet of oncoming barges.
''It's just like the autobahn,'' he said, tapping his throttle. ''Some people are careful. Others are more crazy.''
As the Ehrenfels nears the village of Kaub, it slows to a crawl. The water level here dropped to as low as 13 inches in places late last month. Pfalz Castle, a pint-size medieval fortress built on a rocky spit of land in the middle of the river, originally to collect tolls from passing ships, nearly became a toll booth on a sandy highway.
Mr. Engelhart has it easy. The shallow draft of the Ehrenfels does not vary that much, regardless of how many passengers are on board. Barges, which constitute a majority of the Rhine's traffic, can sit high or low in the water, depending on the weight of their cargo.
For shippers in Dutch ports on the North Sea, that means calculating how heavily they can load their barges for a journey that could take them as far as the Swiss Alps. Sometimes, the barge operators lose their nerve on the way, stopping to lighten their load or to call for a local pilot.
Mr. Fendel sails to the town of St. Goar, where his tug ties up to a Dutch barge laden with coal. As he tosses the line to a crew member, Mr. Fendel also hands over two bottles of Reisling wine, which come from his family's vineyards on the steep hills overlooking the Rhine.
The Fendels say they have guided ships along the Rhine since the 1600's. But the family firm, run by Mr. Fendel's distant cousin, Karl Ferdinand, long ago diversified into wine making.
For Karl Ferdinand Fendel, an ebullient sort who prefers tapping wine casks to tugging barges, the drought is a mixed blessing. He does his best business during floods, when the Rhine's currents are treacherous. On the other hand, the lack of rain has made his wine harvest unusually promising.
''Kleiner Rhein, guter Wein,'' Mr. Fendel said, using a local saying that translates as, ''small Rhine, good wine.''