Children's clothes were washed away. An evening barbecue was doused. An old couple sitting on a bench were engulfed by water up to shoulder- height. Shocked diners in a beachside restaurant watched their food being consumed by the waves. Two swimmers struggled hard to get back to shore.
Frightening though last week's waves were, they were by no means the first to strike beaches in East Anglia recently. The cause is neither wind nor weather, but man-made: the wake from a giant, high-speed catamaran which, in June, started ferrying holidaymakers from Harwich to the Hook of Holland.
The Stena Line's Discovery is one of the world's largest high-speed ferries - the size of a football pitch, it carries 2,000 passengers and 375 cars at a hurtling 40 knots. Stena UK Director Gareth Cooper describes the vessel as "a block of flats that can travel at 50 miles per hour."
It is so fast that it has cut the usual journey time by half, to a mere three hours and 50 minutes. The drawback, however, is its surging bow- wave, which has been racing onto the Suffolk coast unannounced twice a day.
The ferry's impact is so powerful that, 10 days ago, a woman walking on the beach in Aldeburgh was knocked off her feet and dragged into the sea by a sudden surge caused by the vessel. She managed to swim back to shore but was bruised and badly shaken.
On the same beach, James Keen's fishing boat was damaged by a sudden undertow which wrenched the helm out of his hands. Mr Keen had seen the Discovery pass by minutes earlier.
Fearful that someone was about to get seriously injured by the twice- daily, unannounced wave visitations, residents and the Suffolk Coastal Council complained to the Port Authorities. Stena consulted the Harwich Haven Authority and the ship's manufacturers in Sweden, and agreed to find alternative routes. Warning signs were also installed alerting people to the dangers of the "freak" waves.
However, it was an alternative route on Wednesday evening, taking the boat close to Felixstowe, that caused last week's wave that wrecked havoc on sunbathers and diners.
Although the Harwich Haven Authority agrees that the incident was a one- off, caused when a mechanical fault in one of the Discovery's engines forced it to slow down below its optimum speed, causing it to sit lower in the water, Stena has now been ordered to keep Discovery well away from the shore, and to ensure the ferry slows right down in the event of any problem.
Stena argues that the Felixstowe incident was exacerbated by unexpectedly shallow water and the calm weather, which started off a wave sequence that was "particularly noticeable". Bob Brouwer, speaking for Stena, explained that the new rules should prevent a repeat of the Felixstowe incident. He pointed out that the Discovery is unusual - only three catamarans of that design are in service in the world today, adding that an independent expert had been flown over from Norway to see if there was anything else that could be done.
But Jane ver Haest, owner of the seaside restaurant hit by the waves on Wednesday, is not impressed. "The ship was running late and they were going too fast. The pilot had absolutely no concern for human life."
Mrs ver Haest's concerns were echoed by Charles Manning, who was walking his dog when he heard the shouts and screams coming from the beach. He said: "They were driving recklessly, coming in too fast. If a little kid had been involved, we could have had a tragedy. We shouldn't have to clear the beaches every time a ship comes past."
Traders are also worried that tourists who hear about the boat will stay away from Felixstowe beach. Anglia Water has just spent pounds 14m cleaning up its stretch of water in an attempt to make it safe for swimming. Mrs ver Haest is waiting to see whether this week's wash-out will have a lasting effect on business. "Previously, the terrace was one of our best features because we were closest to the beach. Now people might be scared to eat here in case they end up getting drenched."
Further down the coast, at the Orford Ness nature reserve, there are concerns, too, about the damage already done by Discovery. Staff at the National Trust-owned reserve claim that the super-boat has been causing erosion of the area's beaches. On one occasion, last week, a portion of the reserve's shingle beach was washed away by a large swell just minutes after Discovery left its port, running an hour late to schedule. The section of beach was transformed from a gentle incline to a steep slope.
Local coastguards have been keeping a close eye on the waves, too. "Our fear is that a child or elderly person could be knocked over or swept out to sea," said spokesman Philip Ebdon.
From here on, it seems, a lot of people on the coast will be watching the Discovery very closely indeed.