Pick Time Attack - Venice Canals .
Might be easier to pick a Novice Boat like Vector as they go slower, gives you more time to see these tricky little b*stards.
Gondola 1 - Immediately from the start the course bends right, you'll see two blue boosts, its just to the right of the second blue boost.
Gondola 2 - Carry on through the course, under 3 bridges (the second one opens above you just for knowing your in the right places sake) and take a left through the tunnel to the left of the yellow ramp. You'll see a red boost and the second Gondola is just to the right.
Gondola 3 - Carry on past the two yellow ramps, it doesn't matter which of the three paths you take but i stay central and drop down just before the green ramp with the yellow arrows. Drop down the next waterfall, you'll see a blue boost in mid air and the Gondola is on the left before the course bends sharp right.
Gondola 4 - The course naturally takes you up the short rapids untill a course direction marker points you to go left. Take said left, keep to the right of the course (and not through the dark tunnel on the left full of wooden posts). Look for the bridge opening just in front of you, the 4th Gondola is immediately after the now open bridge and on your left hand side.This is a slightly tricky one if your going too fast so make sure your just trundling along.
Gondola 5 - The course takes you up some more rapids and you are now nearing the end of your first lap. In front of you, just before the finish line are a blue boost on the left and a red boost on the right. The next Gondola is immediately on the left after the blue boost but before the finish line. You can get this on the next lap if you miss it this time round.
Gondola 6 - On Lap 2 now, the course bends round to the right but things have changed. On your right there is a house that has collapsed into the lake. Stay to the right, either boost jump over the house or stay hard right and you will glide over the submerged roof (thanks myoptikakaka). Once over and into the new canal, stick to the left. Smash through the little wooded piers and you should naturally get the 6th Gondola, its immediately after the last wooden pier but before you go up the steps.
Gondola 7 - Last one. Past the single yellow ramp, instead of taking the left tunnel that got you to Gondola 2 go straight on. The course bends naturally to the left, the last Gondola is immediately on the left hand side just before the old looking building. This is a sharp corner so it may help to take it wide to the right and turn sharp to the left to give you more chance to see the Gondola.
Achievement unlocked! I hope this helps, it took me a few goes to find all 7.