I was onboard the Humboldt 4-11 Sept 2017 and we had numerous whale shark encounters, however, back on land, I was hearing from other liveaboards we had seen in the north, they had none. Last time I was there was the same week in Sept a couple years ago. Again, no sightings reported for some time nor after our trip. Guides dropping in at the right spot can make a difference. William Astudillo on the Humboldt is my favorite dive guide working in Galapagos.
This was a really fun moment William captured on film. Thought I had, but my battery went dead. We had a naked diver doing his 100th on this dive, but it was a bull sea lion body slamming a Galapagos shark that stole the show. Off screen and behind us is a rookery with many juvenile sea lions. 3 days later, from a panga, I saw a Galapagos shark in the same location. Either they've had some luck or, like my dog who still believes she can jump up a tree in pursuit of a squirrel, they don't have it in them to give up.