The agency won the business following a competitive pitch process managed by Creativebrief.
Hooper Galton has been briefed to develop a launch campaign for the brand, which will be introduced in the UK next spring. The work will encompass TV, press, outdoor and online ads. No one at Hooper Galton would comment on the win.
Isklar, which claims its product is derived from Norwegian ice, is also looking for PR, media and sales promotion agencies. Peter Krough is the brand's director; Dean Ingram is its UK country manager.
Isklar's rivals in the UK premium water category include Evian, Vittel and Perrier.
Danone Waters, which owns brands including Evian and Volvic, is to boost its promotional spend by 15% in the UK next year in a bid to increase consumption of its products.
The water market in the UK grew 11% to £643m in take-home sales last year, according to the Britvic Soft Drinks Category Report 2007. It was also the fastest-growing sub-category in the on-trade, up 28% to £75m.
Bottled water accounts for about 20% of the UK's total soft-drinks market by volume, compared with more than 50% in all other European countries.
Last year the UK consumed 22.7 litres of water per person.