I'm sorry for the guys this happened to but isn't it obvious that the channel was blocked?
Branches sticking up from the tree they hit kept me from choosing this channel. Left channel requires a bit of tricky rowing or getting out but is not a big obstacle or safety hazard. Advice to beginners? If you're not sure of the way through, get out and look before committing the boat and...walking a bit is better than swimming!
Be safe!