Secret #1: Hidden by Seaweed
The first secret is fairly early on in the level. When you start the level and make your initial drop into the water, if you keep going downwards, you will see some seaweed against a wall.
Behind the middle seaweed is a crack in the wall - it is harder to see than most. Send a rocket that way, and a new room will be revealed. You will see an area behind a fence with an additional scuba gear if you need it. This is not the secret, however.
You need to go into the area behind the fence, and surface in the water there. An additional room will be in here with several Octabrains and slimers. There is a ledge on the far side of the room. You need to get up on the ledge there to be credited with the first secret in Flood Zone. There is also a Devastator weapon on the ledge to get as well.
Secret #2: Empty Secret
The second secret is immediately to the left of the blue key. When you grab the blue key, the wall to your left is an invisible one. Jump into it to get the second secret. There's nothing actually in here, it's just a ledge to shoot out at some Enforcers on a rooftop on the other side of the level.
Secret #3: Hidden Room
The third secret is near the locked red key door. When you are up there, there is a small ledge off to the side that you can jump off and get to.
Once you get on the ledge, take out the trooper that was here (if you didn't do so already). Grab the ripper chaingun, and then turn to your right. The rightmost window is a secret one. Open it. Go in the room to claim the secret as well as some chaingun ammo.
Secret #4: Up on the roof
The fourth secret in this level is behind the locked yellow door. When you enter the locked yellow door, the way through the level's path is down. However, if you go up, you end up on the roof of the building. You will see a ledge up here with an Atomic health on it. Behind the Atomic health is a secret wall. Open that wall to reveal a tiny room with a jetpack in it. Go in there to get the jetpack to get the fourth secret.
Secret #5: Crates!
The fifth secret is right past the locked red key door. You will see a sign on the crates that says "Hard Hat Area". This is actually a hidden switch. Go use it, and you will see an area open up on the side of the crates that was not there before.
Going in there will reveal an Enforcer, and some health. Take out the enforcer, then go grab the health for the final secret on this level.
Hidden features Edit
The following hidden features are not counted as secrets.
- When you reach the cliff edge at the very beginning of the level, fall directly into the water below. Swim on the surface of the water. Near where the building's shadow meets with a lighter section of water, Night Vision Goggles will be obtained by swimming near the cylindrical outcropping of the building. It is not clear whether these Night Vision Goggles were placed here by mistake or as a deliberately hidden feature.
Easter eggs Edit
- Near the ledge with the Blue Access Card, there is a small waterfall pouring out onto the sunken building. Steam is emitting from the top of the waterfall. Using the Night Vision Goggles, the message "ANAAL OOTHRIC" can be seen on the wall to the left of the steam. This is the Gaelic term for "dragon's breath."