But these weren't sharks, though the name sounds almost as deadly; we were adrift in a pod of killer whales in the Canadian Pacific. And far from feeling any frisson of terror, our enthusiasm was boundless as the whales leapt heavily out of the water for a split second before flopping back in with the gargantuan grace of a jumbo jet coming in to land.
There were shortcomings. It was not a picture-perfect day - the clouds were low, the winds high, the seas choppy and extremely cold - and there wasn't a toilet within hours. You could hang off the back of the boat, but as we were dressed in thick boiler suits, and the temperatures were sub-zero, it wasn't a tempting option. We simply crossed our legs and paid attention to the whales.
They were well worth the effort. They made leaps out of the water - an exercise known as "breaching" - and some swam within feet of the boat, surfacing briefly and then disappearing again into the dark water. Of course there were some disappointments; none of the whales close to us leapt completely clear of the water in the manner of Seaworld-type shows, but that is the pay-off for watching wild rather than trained creatures.
You also get the opportunity to play a great guessing game. You watch where a whale last disappeared into the water. Then you imagine it swimming below the surface, try to estimate the speed and direction it is going in, and then stare hard at a patch of water in the hope that it will emerge right in your line of vision. You hardly ever get it right, but with so many whales swimming around there's usually some activity not too far away.
We were floating in a pool of about 20 whales - a well-documented family resident in the area. The tour operators who take you out to find the whales are not allowed to approach them any closer than 100 yards. But when the boat drivers turn off the engines, more often than not the whales will swim up near you.
The tour groups are based on Vancouver Island, mainly in the city of Victoria. They try to keep track of the whales day by day, and some will even offer a money-back guarantee of seeing them. Many claim to have a 90 per cent success rate.
There are two main types of killer whale, resident and transient. Resident whales spend their entire lives in a relatively small area, enabling them to be fairly easily found, and eat only salmon. Transient whales are harder to track down, and eat seals as well as salmon. On one occasion, our guide informed us, a seal leapt on to the boat in an attempt to escape the hunger of a transient. It perched at the front for a few minutes, but when its fear of the whale, who had disappeared, began to be replaced by fear of the occupants of the boat, it slithered back into the water - only to be greeted by the whale's jaws as it rushed up from its hiding-place in the deep.
The resident pods, which live a few miles from the shore of Vancouver Island, are closely monitored in an attempt to learn more about these creatures and so be better able to conserve them. They can be recognised by their fins, which are of varying shapes and sizes, though it takes a trained eye to differentiate them. The pods are made up of 20 to 80 whales. They are led by the oldest female, who may be up to 80 years old, but the males are the larger sex, with fins that are noticeably longer.
Their long lives make them harder to study than most other animals, so despite close observation, much of their behaviour is not fully understood. Breaching, for example, seems expend a lot of energy without any particular purpose. One theory is that they leap out of the water to relieve an itch or shift parasites that may be taking up residence on their skin. The whales are known to go to "rubbing beaches" where they rub their sides and stomachs on the smooth rocks and pebbles. I'd like to think they do it for the sheer fun of it.
Learning about whales and hearing stories from the guide was enjoyable, but we took infinitely more pleasure from admiring the creatures as they breached, puffed, and then disappeared into the icy ocean. If it hadn't been so cold, we would have stayed there for hours, wasting less time taking shaky photographs and spending far longer just appreciating the whales. But we had to get back - leaving them in peace without the noise of engines deafening them and boiler-suited tourists gawping at their every move. They must have been glad to see the back of us, and we were glad that, apart from having to put up with a few boats every day, they were free to roam their territory.
There's a great deal of competition across the Atlantic this summer - but it's mostly between would-be travellers searching for seats. The scheduled airlines flying from the UK to Vancouver are Air Canada (0990 247226) and a British Airways/Canadian Pacific codeshare operation. Air Canada has 12 flights a week from Heathrow to Vancouver, while BA and Canadian each operate one service per day.
Scheduled fares to Vancouver in June are reasonable: until the end of this month, the BA/Canadian fare through discount agents is below pounds 400 return. In July, this rises to more than pounds 650. Charters from Gatwick on Air TransAt cost as little as pounds 237 in June through agents such as Quest Worldwide (0181-546 6000), rising to a summer peak of pounds 567.
Visit Canada Centre, 62-65 Trafalgar Square, London WC2N 5DY (0891 715000)