Well it's not very fast.

but loud

you will need it when it comes by and you are in a gondola

#1 Not very fast for sure but Venice is not very big anyway (only 3 x 5 kms)

Tarzambulance save jane aiaaaiaiaiaaaa

Who needs fast? This is picturesque!

The one problem with Venice is.... it stinks!

Lol, Tarzan to the rescue! Wow, an annoying sound!

The typically demented expressions of tourists nearby... priceless.

My own theorys:

Why its not fast, if it goes faster the waves could reach up to maybe open windows, or tip/fill other boats.

Why its so loud, other boats in the way cant move to the side as fast as a car so if the siren is louder they will get more time to move out of the way. (They will hear it further away)

#1 Yea, but did you see the waves it made at this speed? Imagine it going faster.

#1 Considered that in Venice you only move by foot or boat this seems pretty fast to me! Speedboating through the channels is not an option because other ships (rowboats and traghetto ferry boats) are very slow and cannot stop or move easily out of the way, for sure you'll ram onto someone. Not to mention there are also low round-arched bridges where you have to pass exactly in the middle and the water level is not constant during the day.
#2 About the loudness i don't care since saving a life is worth waking up an entire city if you ask me.

#1 ...and this is a pass in one of the major corridors of the city http://www.youtube.com/watch?v=w0fQI_8glnE
Seems slow to you?

#7 Yes, it stinks a lot

#10 #11 The boat won't necessarily make greater waves at greater speeds. If it starts planing, it'll actually produce much smaller waves.

#13 You wont get a boat planing in there..

#13 as #14 said, you can forget about planing. The max speed he could be going would make bigger waves.