Operation: Tidal Wave is a linear infection map made on the dev map Riptide. I wanted to challenge myself to see if creating such a map would be possible on a preexisting one and so this is the result.

Infected Traits"
Alphas move a little bit slower than regular infected but have a small regenerating shield that makes them a bit more durable. They also have the ability to ground pound which doesn't do much damage, but allows them to close the distance and easily confuse a closely huddled group of humans.
Regular Infected move much faster than their Alphas, but they are a bit weaker. To compensate, the infected can use their thrusters twice in quick succession to try and avoid bullet fire.

Below is a complete walkthrough of the entire map so if you don't want to be spoiled, don't read below.
Walkthrough"
Initial Starting Area
When you spawn in as a human, you will be prompted to turn a switch that will open up the pipes in front of you to reach the first phase.

In doing so, you will also be releasing the infected that are housed right next to you so be careful and watch your back when leaving the initial starting area.

Hidden Halo 1 Pistol Location:
When leaving the initial area through the pipes, if you happen to go through the right one and look to your left, you will see a Halo 1 pistol lying behind a slightly broken grate.

It'll be difficult to obtain if your fellow survivors keep pushing you through the pipe along with the infected chasing you from behind, but if you manage to get it, it will prove to be very valuable.

Phase 1
After leaving the initial starting area, you will be prompted to activate a button that will open the door after a certain amount of time. During this, all you need to do is holdout and wait.

Weapons:
1 SMG
1 Shotgun
1 Grenade

Phase 2
As you run through a narrow corridor, you will need to call down an elevator to push a button up top that will unlock the door.

Only one person is needed to push it allowing everyone to progress.

Weapons:
1 SMG
1 Shotgun
1 Assault Rifle
1 Magnum
3 Grenades

Hidden Grenade Launcher Location:
As you fight off the infected horde, you might notice in a corner buried in the sand is a grenade launcher.

Phase 3
When you leave the elevator room, you'll plop down into a submerged area. You'll have to enter the draining chamber to drain out all the water and move on.

Make sure everyone is able to make it inside before activating the button. Otherwise, those who don't will have to wait it out.
Once you exit the chamber, a switch will be waiting to be activated and open the door.

Don't feel so safe as you wait for the door to open. The infected are able to drop down from a hatch up top as well as from around the corner near the SMG.

Weapons:
1 Shotgun
1 Assault Rifle
1 SMG
1 Grenade

Phase 4
The final phase before the final holdout room require the most teamwork and communication. When you approach the gate that's preventing you from escaping, you'll notice it's mechanisms have been damaged.

Some people will need to search the rubble near it for a pipe to replace the missing part.
At the same time, it is recommended that some humans stay up top and fight off the impending horde.
Once the pipe is replaced, you will need to wait for the mechanics to boot up again allowing the humans to move into the final holdout room.
Weapons:
1 Shotgun
1 DMR
2 Grenades

Hidden SAW Location:
Although you're guided to run up the ramp with your team, if you move along the ground and around the generators, you'll find a SAW resting on some sandbags.

Final Holdout Room
Once the gate open, run to the final holdout room where you need to press a button that will slowly close the door.

The only objective in this final phase: Survive.
Weapons:
1 Assault Rifle
1 Grenade