Codebreaker

Here is the way to crack the code if you want to know:

Spoiler: Hint #1

Pipes are key!

Spoiler: Hint #2

The correct order of underwater corners is indicated by the number of pipe pieces found in them. (Not including the boundaries)

Spoiler: Hint #3: The Big One

The pipes on the outside walls indicate which levers need to be flipped to reach each corresponding underwater corner. For example, to reach corner 1, flip all levers that have a one-length piece of pipe on their outer wall. (Ignore pipes on the central part of the island.)

Hopefully I'll be able to make better and more rewarding/intuitive secret-code levels in the future. I'm still new at this, after all.

Solved it, read the spoilers, still don't get it.

Like @Block builder, I solved and read the hints but I don't get the code...

Hmm, that's interesting. I guess my level worked as a puzzle but not as I meant. Btw I just realized that what I call pipes are actually called rails.

I've tried this numerous times but it doesn't work for me. Can you possibly share more of the solution? Thanks

Oh no, not this level. So, full disclosure, I don't like this level of mine; it was an early level I made when I was still a new creator with no idea how to make a good or playable level. This level was purely hidden and not much else, and I've since moved away from that. Sometimes hiddenness in a level can be okay, but when I was just starting out I tried to use it as a substitute for logic or puzzle-solving. While there are a few people who may enjoy hidden levels, the vast majority of players (including me) tend to get frustrated by that sort of thing. And hiddenness in general is not a substitute for logic; in my opinion, my favorite kinds of levels are able to hide a path in plain sight, not by sticking something in a dark corner or underground, but by causing the player to overlook something right in front of their nose.

With that being said, I decided not to delete this level (as well as the others in this album) because it is sort of like part of my history as a level creator. It documents my journey in level-making, and I love histories and how-people-started-out kind of stuff. If I had to rate this level of mine, I'd honestly probably rate it pretty badly, and that's only if I would have been able to solve it with those cryptic and badly worded hints. I wouldn't recommend people to play the levels in this particular album of mine except to see where I started, hence the name "First/Not-So-Good Levels". My other albums are the levels I've made that I thought were actually decent. Below I've attached an image of how the solution was intended to work out. Let me know if the visual hints are helpful; if not I can make a solution video, but it's really hard to understand the "code" idea from watching a video of the solution. (On a side note, it's intriguing how many new creators start out with zapper levels and code levels, myself included. )

Spoiler: Visual Hint Picture

https://drive.google.com/open?id=1klgPnScf7AmfnTOYBVwUseFEWXkrEWrJ

Please don't feel any need to explain - if I could do 1/10th of what you did I'd be very pleased with myself indeed! I finally completed it -- but I would never have managed to do so without your "cheat sheet"

A bit confusing and I definitely needed the hints. Initially I became totally frustrated and solve the level with the TOA on to the win block but since that was not the intended solution then that is cheating so I had to go back and solve the way you had intended. It was still fun and much better the intended way.

Spoiler: VS (v1.6.2)