On our sail north from the Azores, we saw whales most days. On one occasion 3 huge fin whales followed us for 50 minutes. Difficult to estimate their size but probably around 20+ metres; certainly made our boat feel very small.
The video clip is a bit shakey - but we were more than a little apprehensive as they came so close to the boat and stayed with us for a long time. The turquoise colour is the under-belly of one whale that went under the hull.