Great Barrier Reef Foundation chairman Dr John Schubert says a controversial federal government grant of $443.3 million was necessary to protect the reef as it faces the threat of climate change.

Dr Schubert is one of seven foundation representatives giving evidence to a Senate committee in Canberra on Tuesday.

The inquiry is seeking details on why the government granted the six-year funding stream to the small not-for-profit foundation without going to tender, and how it plans to use the money.

"You asked was I surprised ... but my overwhelming initial reaction was: 'This is fabulous news for the Great Barrier Reef. This is what is needed'," Dr Schubert said when asked about his reaction to receiving the grant.

He said the reef faced ongoing threats against climate change and needed to be protected.

He "quickly" came to the conclusion that the foundation had the capacity to leverage the funding to raise more money from the private sector to protect the reef.

Former prime minister Malcolm Turnbull and then-energy minister Josh Frydenberg were at the meeting with Dr Schubert when the foundation was offered the grant in April.

Dr Schubert said he has not spoken to Mr Turnbull since the meeting, while other directors, including respected marine scientist John Gunn, said they believe the foundation was chosen for the grant because of its "track record".

Dr Schubert said the foundation "recognised very openly that climate change is the greatest threat to our Great Barrier Reef".

"I think the vast majority of Australians now understand that the reef really is threatened and is already being damaged by climate change," he said.

Critics of the grant have raised concerns about potential conflicts of interest and commercial interests, given the foundation has a number of corporate backers from the resources sector.

Foundation managing director Anna Marsden said there had been no negative impact on operations or support since the announcement, despite the criticism.

The foundation has told the inquiry it had projects due to start next year.