In 2010, I had an unexpected/serendipitous whale shark encounter, although not quite like the one in this video and story.
We were in South Africa, diving at Sodwana Bay. About half way to our planned dive site, the captain stopped the boat and told us to get in the water, because there was a whale shark. We got to spend several minutes snorkeling with it. Very special moment. Eventually, we got back on the boat, and continued to our dive site.
The funny thing was, that there were two boats that went out at about the same time that day. We were planning a reef dive. The other was specifically looking for whale sharks to dive with. They never found one. We got to see the whale shark, as well as complete our planned dive.