Two solid FTSE stocks, covered by a total of more than 50 analysts, fell by 15% in a day during the first couple of weeks of January. It would have been downright spooky for any of Carnival’s crew of followers to have predicted the bizarre sinking of the Costa Concordia, yet it is astonishing that nobody anticipated the news from Tesco. Both companies dominate their industries, both have suffered severe reputational damage, but the longer-term impact on each is likely to be dramatically different.

The loss of a huge new cruise liner is obviously far worse than the admission that profits might not grow for a year. Any loss of life, however small in the context of thousands of passengers successfully rescued, is a tragedy for those concerned. The realisation that the sea is always capable of springing nasty surprises will at least dampen the enthusiasm of holidaymakers to go cruising.

The disaster will provide a fine excuse to explain why we’re not going this year, even if shortage of cash is really a more powerful reason for many. Even those who do take to the seas might decide that boarding these floating blocks of flats along with thousands of others is just too risky, at least until the operators devise a better way of getting them off in an emergency. At the very least, there are going to be some terrific offers for those prepared to brave the waves.

Compared to a disaster at sea, Tesco’s news barely warrants a ripple, but this company has ridden serenely through economic storms in the past, and the question now is whether it is finally holed below the waterline. Even asking the question feels slightly ridiculous. For 20 years Tesco has not only blasted the opposition, it has terminally damaged businesses which didn’t realise they were in competition, like Game Group and HMV. Its supermarkets have marched all over Britain, and into Asia, Europe and the US.

What spooked the shares was the uneasy feeling that the game might be up. The UK business has been used to pay for the foreign adventures, and the opposition has caught up. Worse, all that wonderful real estate looks less like a comforting asset. It might even become a liability as shopping moves on-line. Tesco’s trading update would have looked even worse without the 14% growth in on-line sales. The Ocado experiment may have failed, but the internet seems likely to rip the bottom out of retail shops, and in a semi-stagnant economy, clicks’n’mortar might not cover a falling footfall through the expensive real estate.

Tesco has shown that it is not quite the well-oiled, all-conquering machine that it had appeared to be for so long. It now plans “an even better shopping trip for customers”,  a slower rate of expansion and no more than the occasional new hypermarket. The outlook statement betrayed uncertainty. It’s infectious. The shares have hardly bounced since the fall that followed the figures, despite the purchases from Berkshire Hathaway and Tesco’s chairman.

The Carnival price is also looking pretty bruised, and the pictures of the stricken ship will keep popping up long after it’s been salvaged. But while the business model may be listing badly at present, it doesn’t look likely to capsize. There is no systemic problem; the Tesco shareholders must wish they could say the same.