I just returned from a 10 day visit to Galapagos - and everywhere I turned, people there were in agreement.  The footage captured by the BBC was simply extraordinary.   I lived in the islands for 4 years and have been on a few cruises. Never have I seen a snake.   It turns out that the rocks, particularly on Fernandina island, are slithering with them.   All they need is a little temptation to coax them out.   See the footage here: 

https://www.youtube.com/watch?v=B3OjfK0t1XM