I was not sure we would be as lucky as other people in the comments, but I confirm it's real! We saw a bunch of hump back whales (almost ten in total!!), including a mommy with her baby; and also a gigantic fin whale, plus several Risso's dolphins, awesome!
Few side notes: motion sickness is not a myth, I'm usually not subject to it but it was hard as the trip was long and the boat moving a lot, so towards the end I got sick. Do not hesitate to take something beforehand to prevent that, it's not 100% effective but it can help (there are bracelets, pills, ...).
Second note: don't expect the whales to jump and do crazy things, you will most likely see their back, fin, and blow, which is impressive and a great experience to live! I'm just saying to avoid any disappointment ;)
Thanks to the crew who was nice and know well the ocean and the animals.