Stephen Fry can hardly contain his excitement when he catches sight of the mighty blue whale - the biggest creature known to have lived on earth - off Mexico's Baja peninsula.
The blue whale is almost as long as a Boeing 737 and needs so much food that, in terms of weight, it could eat a fully-grown African elephant every day.
Fry and zoologist Mark Carwardine have been tracking down some of the most endangered animals on the planet in a six-part series.
Last Chance to See goes in search of the blue whale on Sunday 18 October at 2000BST on BBC Two.
Previous episodes are available at the
Last Chance to See