river ferry to O2

Afternoon (GMT) quick question for those who know London

Travelling to the O2 from Paddington and was thinking ways to avoid the unbearable hell of getting home with 20,000 other people on the tube when Tool finishes. A few people have told me in the past that the best way is to get there and back is a river ferry from Embankment to Greenwich. Never done it before so wary of getting involved with boats but looking at the website they run late (much later than I thought) so I'm tempted. Is it worth it? Or will 10,000 other people be thinking the same as me and I should stick to the tube. The thought of skipping onto a boat and travelling down the river relaxing with a beer to each destination rather appeals to me. Answers not on a postcard, but right here on watmm. Thank you.

oh there's a river nearby? then I think the answer should be obvious. skip the boats and 

sorry beer brother. no clue on your question.