Photos and video shared by the group had showed Hobson swimming with dolphins on his journey.
A police media spokesman told Stuff that they responded to a report of a sudden death at Mana on Friday evening.
There was no further information on the cause of death.
Tributes from international organisations have emerged online for Hobson including from the Marathon Swimmers Federation, the British Octopush (underwater hockey) Association and the International Swimming Hall of Fame.
He was acknowledged for his swim across Lake Michigan in 2018 and his involvement on the organising committee for 2006 CMAS Underwater Water Hockey World Championships in Sheffield.
At least 130 people have swum the approximately 23km distance across the strait, according to a website chronicling attempts across the dangerous waterway between the North and South Islands.