Whyyyyyy?
To hedge your bets with "no evidence" that these people managed to navigate shallow sea waters to a nearby island, which they had inhabited for thousands of years and knew like the back of their hand, seems… unnecessary? Disrespectful?
I mean, we already know Mesolithic "hunter gatherers" managed absolutely mind-boggling feats of both art and engineering. More is becoming known every year, and it consistently amazes us in the direction of "No way!"
Building a boat / canoe for island-hopping over well-mapped marshes and shallow seas is the least of it.
If speculate on "no evidence" we must, my bet goes 100% in the opposite direction: The gradual increase in sea levels prompted new inventions and spectacular constructions, now lost to time. As far as speculations go, it seems a safer bet than "couldn't paddle".