The boat, which is required for essential marine conservation work, is used for accessing areas difficult, and at times impossible to reach by foot, such as Keyhaven Marshes and Pewitt Island.
It will also help the Trust monitor local seal populations in the Solent as well as keeping a record of winter bird counts.
Hambrook Landscapes managing director Norman Hambrook explained: "We wanted to become involved with a local charity especially an organisation such as the Wildlife Trust not only because of our commitment to supporting our local community, but also because we want to help our customers see how environmentally beneficial it is to encourage wildlife into our gardens."
The firm is in the process of re-building show gardens at its Titchfield Garden Centre, including a wildlife garden being planted with the help of the Wildlife Trust.
Hampshire & Isle of Wight Wildlife Trusts' Marine conservation manager Jolyon Chesworth said: "It's great news that Hambrooks is supporting our vital marine conservation work. Much of our most important conservation marine life lives in difficult to access areas and we have been hampered in our efforts to survey and monitor it. The new boat will enable us to reach these areas and, together with our underwater video cameras, open a window to what is going on beneath the waves and in our most isolated stretches of the south coast."