"Look! Out there!" a mother called to her children, who were scampering along the promenade at the North Yorkshire resort of Filey. Excitement mounted as the family peered at the high tide lapping against the sea wall. "There it is!" Binoculars were produced and focused, followed by a sigh of disappointment: "Oh". Instead of the wildlife they had been hoping for, the family found they were looking at me. It's not everyone who has been mistaken for a seal.

I was later informed of this misapprehension by my wife, who was also walking along the prom, burdened by my towel and the clothing I struggle into in a not-always-successful attempt to retain my modesty at the end of my daily swim. While I cannot claim that my plodding breaststroke bears much similarity to the lithe grace of a seal, the mistake of my observers was understandable.

An aquatic mammal at Filey is unlikely to be human. Few people feel the urge to go beyond their ankles into the North Sea. Unlike the Cornish Riviera, for example, it does not hold much allure for bathers. Just saying the name makes some people shiver. This is unfair to the North Sea because there is very little variation in sea temperature around Britain. On the day I am writing these words, the sea temperature at Penzance is 15.5C, while at Filey it is a balmy 15.3C.

Though the initial immersion comes as a shock, you don't notice the cold after the first couple of minutes. Since acquiring a house on the Yorkshire coast in 1996, I've been swimming there for several weeks each summer. It seem to be getting progressively warmer, though no one would mistake Filey Bay for Cap d'Antibes.

Particularly on still days, sea swimming can bring me close to ecstasy. Supported by saline buoyancy, it is the closest I'll ever come to flying. The morning smell of the water is one of the great fragrances, if occasionally tinged with frying bacon from hotel breakfasts.

There are a few drawbacks to this watery paradise. Seagulls take an uncomfortably intense interest in you, diving out of the sun to examine the large, white and potentially edible intruder. Last year, I had an unusual encounter with the murderer featured in a Sherlock Holmes yarn, whose victim "had been scourged in some savage, inhuman fashion".

In my case, the sting of the lion's mane jellyfish (actually it looks like a bit of old brown carpet) was more of an irritation, though unpleasant enough for me to seek help from a lifeguard. "We've had a lot like you," he said. "I've got something for that." Instead of the sophisticated antidote I was expecting, he produced a large bottle of Sarson's Malt Vinegar. I applied a few splats but it made no difference, apart from making me smell like a very large chip.

On days when the sea erupts into violent life, I used to plunge in regardless until I had a particularly ferocious encounter with the breakers. Getting bashed up is (one hopes) an unusual experience for a middle-aged chap. Staggering out after my salty assault, it was surprising to find life proceeding normally with ices being licked and sandcastles under construction. A more surreptitious threat comes from the sea-fret, a mist that can envelop the swimmer with surprising speed. Once I continued swimming, relishing the way that Filey was rendered mysterious and exotic by the haze, until I realised that all I could see was the flashing orange light of a refuse cart.

Usually, the lure of a Horlicks from a beach snack bar draws me ashore after a mile or so. Emerging like a cut-price King Neptune, I am proffered towel, Crocs and helpful advice by my wife: "You've got a moustache of sand".

After a swim last year she forgot to tell me that she'd been using my footwear as a container for one of her beachcombing treasures while I was out among the waves. I doubt if I will ever again insert toe in Croc without fear of encountering a mackerel.