How did Aronnax, Ned and Consiel come to the floating island in 20,000 Leagues Under the Sea?

Disillusioned by Captain Nemo's erratic and dangerous behavior, the three characters in question decide to escape from the Nautilus using a small vessel. Just as they embark on their escape, the submarine finds itself in a massive, deadly whirlpool. The best clue as to how Aronnax, Ned, and Consiel arrived at the Norweigan island is towards the very end of the book's penultimate chapter.
The narrator observes that:

He had not finished the words, when we heard a crashing noise, the bolts gave way, and the boat, torn from its groove, was hurled like a stone from a sling into the midst of the whirlpool. (278)

The narrator is then struck unconscious and cannot tell for himself exactly how their vessel escapes the huge whirlpool, or "maelstrom." Ostensibly, once the small boat is wrenched free from the Nautilus, it was able to rise through and out of the whirlpool on its own course.
This line of thinking requires some extrapolation as the narrator himself admits in the conclusion that he is not sure how he and his companions escaped from the vicious whirlpool and found themselves in a hut off of the Loffoden Isles.