Media in the Scandinavian country named the woman as 68-year-old Ann-Christine Wallenberg.
Swedish tabloid Expressen said Wallenberg had known the Swedish royals since the 1980s and had remained in closed contact with them.
— Birgit Tilert (@BTilert) June 18, 2019
The paper said the Swedish king and queen had been informed of her death.
Wallenberg drowned in Lake Geneva when her sightseeing boat sank during a storm on late Saturday afternoon that brought heavy rain, hail and gale-force winds to pars of Switzerland.
Another man on the vessel was able to swim to another boat and set off flares, Geneva police said.
Three police boats and emergency services rushed to the scene. Police divers later retrieved Wallenberg’s body.
She was taken to hospital in Geneva by Switzerland's Rega air rescue services where she was declared dead.
Wallenberg’s younger brother Stefan Magnusson told Expressen he suspected his sister was entangled in ropes as the boat capsized.