Hi, I went to venice afew weeks ago now and a water taxi from san marco to marco polo airport was 100euros, this was at 8am and based on 4 people with 3 suitcases. if i'm correct, san marco is further away from cannaregio so it shouldn't cost any more that 100euros although that is alot of money for a taxi ride. they are better to travel on, private and faster, but the water bus is just a fraction of the price, 11euro's if i'm correct but does take a little longer! hope that helped xx