Scientific research tag. I believe the story here was that scientist John Calambokidis and his team were in the region tagging blue whales. On the first day they needed to test their methods and telemetry, so they found the most convenient subject...this humpback...and put a suction cup tag on it. Later we spotted it and I took this photograph (already sent to John).
Megaptera novaeangliae with tag 2015 08-11 SB Channel-f-010