Aqua founder and chief executive Francesco Galli Zugaro will remain a shareholder and will continue to lead the line as a standalone business unit.
Aqua currently operates small ships in biodiversity hotspots such as the Galapagos, Indonesia’s Raja Ampat, Komodo, Spice Islands, the Mekong River and the Peruvian Amazon River.
Zugaro said: "Partnering with another family-owned business ensures we maintain a heritage of luxury in our brand.
"With the financial support and expertise from our partners, we are well-positioned to continue our growth and offer our guests unforgettable journeys to the world’s most biodiverse and culturally rich regions while maintaining our core brand values."
Ponant Explorations Group, which is backed by the Pinault family’s investment company Artemis Group, described buying a majority share in Aqua as “a strategic acquisition”.
Herve Gastinel, Ponant Explorations Group chief executive, said: "This partnership aligns perfectly with our vision of excellence and sustainability in the luxury sector.
"It reflects our commitment to offering unparalleled travel experiences in iconic destinations such as the Galapagos and now also river journeys, while preserving the natural beauty of the places we explore.”
He added: “We’re deeply impressed with the exceptional company that Francesco has built over the past 18 years and the unique brand he has developed in the experiential travel space."
Aqua is currently building up to the launch of its East Africa itineraries, exploring the Seychelles and Tanzania, with a particular focus on the Aldabra group of islands.
It comes just a week after no-fly UK cruise operator Ambassador Cruise Line merged with Compagnie Francaise de Croisieres to create a larger fleet.
