The first campaign will be launched in June with a 370,000-volume direct mail programme focusing on 2005 being the RNLI's busiest year to date, with more sea rescues performed than before.
Redevelopment of RNLI's advertising and its offline and online donor programme is also planned.
Amanda Mitchell, RNLI's marketing manager, said: "The fundraising marketplace is becoming ever more complex and competitive and we are very aware that we need to develop more sophisticated supporter communications programmes to take account of this."
Bryan Miller, Whitewater planning director, said what has informed this campaign is research on why donors select certain charities to support.
He said: "The RNLI has no competitors in terms of what it doe but it has to compete with other charities. That is why consumer insight is more important than ever."
Whitewater's other charity clients include Christian Aid, RSPB, RSPCA and Shelter.
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