The Royal National Lifeboat Institution has handed its £2.5 million brief to Proximity London.
Geraldine Cetin, supporter marketing manager at RNLI, said: "We're looking at our entire strategy, ensuring that we have a cohesive communications strategy for all our supporters, which leads to stronger retention and longer lifetime value of supporters."
Proximity will focus on raising awareness of the RNLI's work and step up communications with both new and existing supporters. It will also aim to build up supporter loyalty and encourage legacy giving, communicating with the RNLI's database of 600,000 members and regular donors.
Simon Hall, chief executive of Proximity London, said: "Learning about the dynamic and varied work done by the RNLI has been a humbling experience. We have all been touched by the stories of bravery, tenacity and seamanship and we look forward to making a contribution to the organisation."