The organisation, founded by Geoff Holt, takes disabled people out on the water and gets them involved in steering the vessels and learning about seamanship.
Launched in the city in 2011 with the boat Wetwheels Solent, the charity has grown over the years to other areas and a second boat for Portsmouth is being unveiled today.
Olympic gold medallist Sir Ben will be joined by other city leaders for the event.
Geoff, who in 2007 became the first disabled person to sail single-handed around Great Britain, said: ‘We are delighted that Sir Ben Ainslie will be naming the new boat in our great waterfront city.
‘He is someone I greatly admire and respect, and it is wonderful he will be joining us at this very special and important time for Wetwheels Solent.