Hi mate,
Blackadder aren't exactly the be all and end all of venomous snake training. I recently had to fix their mistakes at a mine near Moranbah - all of their training had been done inside a pit with a total of 4 venomous snakes, and a lot of the information they had been given was wrong.
Venomous snakes CAN climb - in fact, there are several species that are predominantly arboreal. Look up Tropidechis and Hoplocephalus. Then watch this video of an Eastern Brown climbing a tree to eat a rat -
http://www.youtube.com/watch?v=3vPddZK-hQQ
In your defence, the snake in this boat definitely wasn't a Coastal Taipan, a snake that everybody wishes they had a close encounter with (and make up stories to that effect) but very few have ever actually seen. It would have simply been a Green Tree Snake, which come in many other colours.