My Round: What's it all about, algae?

Enjoying a sprinkling of coral in your glass of water? You soon will be, if Mariella Frostrup has anything to do with it

This is surely the most imaginative celebrity product-endorsement in history. The product: Vivatap, a sachet of coral algae harvested off Norway and designed to make water taste better and contribute nutrients to your diet. The celeb: the heavily pregnant Mariella Frostrup, who has apparently shed her allegedly party-girl habits and taken up the role of a clean-living woman. And the meeting of Vivatap and Frostrup produces some very interesting results.

"Water can be one of the most refreshing drinks on this planet," Frostrup revealed at the launch of Vivatap. But she is wary of claiming serious credentials for endorsing her new-founded refresher. "I suppose I am not the most obvious candidate to be promoting water after a debauched past would suggest that another colourless liquid beginning with 'v' was to my taste. Let me assure you I am a changed woman. Ever since George Clooney taught me to hydrate while I dehydrate by mixing my vodka with water, I have become a convert to the benefits of hydration."

Being an ill-informed kind of guy, I had not known of Ms F's soft spot for any particular alcoholic beverage. But I feel fairly sure that she is the first person to be led to water by way of a vodka bottle. Especially under the tutelage of George Clooney. What surprises me more is the product she was involved in launching. I've seen a lot of new improved waters in my day, but this one is different. What's more, it's pretty impressive. The sachets contain three ingredients: the aforementioned algae; chitosan; and an antioxidant in the form of vitamin C. The algae contribute minerals and neutralise acid to bring the water close to neutral pH. Chitosan, derived from the shells of crustacea, has long been used as a water purifier. And the antioxidant removes chlorine.

Does this sound like moonshine? That's more or less what I thought. But I ran a test of Vivatap against my home tap water, both fresh from the spout and, after a resting period for chlorine to dissipate, found that it filled the first role of any intervention in human health: it did no harm. Caveat one: my tap water is delicious, with little chlorine flavour, and therefore not the best test for this product. Caveat two: take the sachet out after the recommended five minutes or the water may take on a strange taste. But if I lived in an area where the water is unsavoury, I'd certainly consider buying this stuff. At £2.99 for 18 sachets, it works out at just 8 pence a litre (for stockists, visit www.viva tap.co.uk or call 0117 959 7040).

An interesting health angle in the Vivatap story is its high calcium content, algae-induced. Jane Griffin, a sports dietician who spoke at the launch, says that calcium in water can play a part in getting this essential mineral into the diets of people who don't get enough from food or milk. And she is not a flag-waver for fancy water: she gets "irritated", she says, by the claims made by some companies for the mineral content of their products. "It would be cheaper to drink tap water and spend the extra money on better food."

This point is worth bearing in mind when dealing with another new entrant into the water race: Alps2O, a pure spring water from Switzerland. This one sells itself as a source of massive quantities of calcium and magnesium, both occurring naturally, and I have no reason to doubt them: the water tastes very strongly of minerals. Some people may like that; I do not. But even if I did, I would take note of Griffin's opinion that "it doesn't matter where the calcium in water comes from". So you may want to buy Alps2O for its flavour, but don't buy it because of any ideas about the superiority of natural calcium. And remember: if it's calcium you crave, there is always cottage cheese.

Top Corks: Beefy reds, ready for beef

Griffin Vineyards Merlot 2003, South Eastern Australia £4.99, or two for £7.98, Majestic Hefty, juicy, spicy plum fruits. Un-serious but a serious bargain at the promotional price.

MontGras Quatro 2002 £8.49, Unwins, www.everywine.co.uk A long-time fave. The foursome: Cabernet Sauvignon, Malbec, Merlot, Carmenère, generously oaked. The result: substantial pleasure.

Barolo 1999, Terre da Vino £10.99 from £12.99 until end of July, Waitrose Youngish, cheapish Barolo - not always something you'd want to drink, but this one is impressively approachable right now.