The doctor told the BBC's Laura Kuenssberg he could no longer look NHS colleagues and patients in the eye and stay as a Conservative.
The first minister's appeal to find "common ground" is rejected by the Scottish Conservatives as "humiliating and embarrassing".
The US says no American forces will go ashore but an unnamed "third party" will drive aid into Gaza.
Peter Smith, 64, was 10 metres off the shore when he was attacked by a bull shark, a local official says.
The presenter thanked everyone for their "kindness and good wishes" and is home with his family.
Customers claim they have lost bets because of "inaccurate" decisions they cannot appeal.
