Hydro Thunder/Catacomb
Starting on yet another long straightaway, this circuit track is entirely based inside great caverns and tunnels. Just before going headlong into the first bend to the lef, you find a 4 second boost towards the right hand side. Around the bend the track has a pair of columnar structures reaching top to bottom of the tunnel. Between them is a hidden 9 second boost, and beyond them on the right of the track is a 4 second boost. Towards the end of the straight is another 4 second boost on the left which leads you into a sharp left-hand turn. At the end of the turn, you find a ramp directly in front of you (or to the left it you took it wide) which conceals a 4 second boost just past it and can be used to boost up to another 4 second boost high in front of it.
If you jump the ramp, try not to boost too much as there is a right turn quickly after it with a waterfall on its left side. Note that this waterfall does not conceal an entrance like many others, so you need to take this turn even though it appears to offer a tunnel at it's top. That said, there is a hidden 9 second boost hanging in the air around here. It's in a different position for different versions and may not be on all versions, so keep a lookout. Around the corner on the right is yet another 4 second boost, but on some versions this one can be difficult to get to unless you are facing it as it appears and this is particularly dependent on the boat you have. The track continues on, heading away from this 4 second boost to the left and into a short tunnel with stalactites in plentiful supply. A 4 second boost is on the left here, but the track heads right shortly after it. Just before you continue around the corner you have a choice. Look straight ahead and you will find a tunnel that you can also jump into. Both paths are worthwhile. In the tunnel you will find a hidden 4 second boost and on the main track you will find a 4 second boost. On different laps get each and on the final lap go through the tunnel.
If you take the tunnel choice, turn left as you go through it. Soon afterward you get back on the main track again as it is a very short shortcut. Almost immediately afterward you will find another choice and again both directions are of use. Both directions have 9 second boosts available. Directly in front you can see a waterfall behind the wall of the track. You can boost over the wall where you will find a 9 second boost and a ramp out of the hidden section. On another lap, preferably the first or last, follow the track as it heads left. Collect the 9 second boost that sits in the corner as the track turns back right to the place where the shortcut will exit. Immediately after where the choice joins again, there is another turn. This time the turn is to the left and on the inside of this corner is another 9 second boost. Get this boost on the first or second lap, as just beyond it is a ramp and then the finish line.
