The breakout at the National Aquarium of New Zealand in Napier, which has captured the imagination of New Zealanders and made headlines around the world, apparently began when Inky slipped through a small gap at the top of his tank.
Octopus tracks suggest he then scampered eight feet across the floor and slid down a 164-foot-long drainpipe that dropped him into Hawke’s Bay, on the east coast of North Island, according to reports in New Zealand’s news media.
From the USA Today account, just becasue I like the name of the book:
"Octopuses are fabulous escape artists, and it's absolutely not surprising that he saw an opportunity to explore and he took it,” said Sy Montgomery, author of "The Soul of an Octopus."