I Am Fish

This can be obtained in the Finale level named aquarium as per the achievement description.

This can be done on the normal difficulty, which I recommend if you still have trouble (like me) jumping out of the water from tank to tank.

There are three fishbowls which you will need to smash to get this. In addition to this, you cannot revert to checkpoint if you smash your fishbowl/die/fall off the desk, after having smashed at least one of the three bowls. Reverting to any checkpoint before breaking any of them is fine but you will need to take your time in between each one to avoid having the restart to level all over again.

All of them are in the same room near the beginning of the level and all three have fish in them. There are two routes into this room. The left route is the one you need and will lead to an empty fishbowl. The right route will lead you to almost the same place, but you will be unable to reach two of the fishbowls going this way. If you jump out of the tank and land in a jar instead of an empty fishbowl, then you must have taken the right route and will need to restart the level.

From the starting point, when you jump into the pipe up high to escape the first display tank, I suggest following the left wall of the pipe. This will eventually lead you to the correct route in to the room. There will be one or two dead ends but just keep following the left wall and you should fall into a tank with several more to jump into until finally you reach the empty fishbowl.

DO NOT skip checkpoint as this always seemed to drop me into the right route instead of the left.

Once you have reached the empty fishbowl, you will have a straight run to smash the first two fishbowls along a long desk. Very hard to miss them if you got this far. I suggest pushing these two off the right side of the desk as pushing them down the gaps on left up against the wall seems not to be a great enough distance to smash them.

Now the third and final fishbowl is on a desk opposite the second bowl. Carry on in the same general direction you were heading to smash the first two. Hug the left wall to drop down onto the top of a desk in the lower part of the room and eventually onto some pipes. Keep taking the right path until you arrive at the desk on the far side of the room. You should be facing the left side of a PC monitor at this point. Turn the camera to the right to see the final bowl. This one can be tricky as it can get stuck between the monitor and the desk lamp behind it if you try to push it forward. I suggest getting behind it, moving it back the way you came and pushing it off the left side of the desk.

If you smashed all three fishbowls without reverting to a checkpoint, this should unlock.

My first guide, so please let me know if there is anything I should add or explain.

Thanks to SK4TE HIGH for advising it had to be done without reverting to checkpoints.

Hope this helps.

Here's a video walkthrough if it'll help. :)

1. Beat all four fish campaigns.
2. Start up the bonus level "Finale".
3. Jump up into the pipe and turn left, then left, then right when the pipe splits.
4. Jump tank to tank until you land in the rolling fishbowl.
5. There will be two fishbowls in front of you on the table. Knock them over.
- Note: If you break a fishbowl, you can no longer respawn, or you won't get the achievement.
6. Continue forward, and turn right when you land on the metal beams. Follow these forward and to the right, to get on the desk that was across the room from the first two aquariums.
7. Next to a computer is an aquarium, knock this one down, unlocking the achievement.