The requirements are:
You have well leveled Deltas
Your enemy doesn't go for a Grenadier Rush
The map is a water map with shores
It is also recommended:
Well leveled Shipyard production time reduction
Well leveled building construction time in Construction Yard
Your enemies rank is at most 1 rank higher than yours
You need to be in Gold League or higher due to (start)-resource requirements
Maxed Power Plant Energy production
Maxed Construction Yard construction range
Build your buildings in the following order:
1 Barracks
HQ lvl 2
1 Power Plant during HQ2 Upgrade
1 Assault Vehicle Factory during HQ2 Upgrade
1 Supply Center (if you got enough Resource containers or are in legendary league, you need to keep 500 resources for the shipyards)
From the beginning, if you decide to use boosts, only boost construction boosts. Make sure to build your Construction Yard to the water.
Only build 2 or 3 Assaults for container gathering, but don't switch to infantry scout boost. This will obviously give your opponent the advantage on land containers, but those you can later get from water will equalize this disadvantage.
The point of such a barebones early-game and your main focus is to start upgrading to HQ2 immediately. The time during which you upgrade to HQ2 is best used to also start construction of your second Power Plant and a Assault Vehicle Factory as both are required to build Shipyards.
As soon as your HQ reaches level 2 you need to place both Shipyards without delay.
After they are built, start producing Deltas immediately. You now want to switch to naval production boosts. Set the gathering point for your Shipyards to where you assume your enemies Shipyards to be. Whatever happens afterwards, you do NOT want to stop producing Deltas, keep the production running.
When your Deltas reach your opponent there are several possible cases which can happen.
Best Case: If your enemy doesn't have any naval buildings, just simply patrol your Deltas on the coast to make sure they don't build any Naval Platforms or Shipyards. Use the other Deltas produced during that time to gather containers. Afterwards gather all your Deltas close to your enemies base but do not attack yet (stay out of their line of sight to not alert them to the rush yet). You should attack his base when your total number of Deltas is somewhere between 12 and 20. (You absolutely want to attack before the enemy has a chance to get out Hawks/Vertex).
Normal Case: If your enemy has a Shipyard and is currently building a Naval Platform you should focus your attention first on the Caimans already built, the Naval Platform second and the Shipyard last. Now you can secure the water, gather the containers and prepare to directly attack your enemy from the beach. Usually, your enemy trying to go for naval means that they are only able to produce Hawks/Vertex later than usual, but this doesn't mean you shouldn't delay an attack on the base too much, as them training Grenadiers can seriously hinder your attack.
Worst Case: Your enemy goes for a naval build and already has a Naval Platform built or you can't keep the platform from being finished. In this case retreat, gather the containers which you can get. Keep producing Deltas and try to catch any Caiman trying to scout you before they reach your Shipyards. You now want to just build up a big Delta army, go on land and attack the enemy from there, therefore completely bypassing their navy. If this happens and if you have the resources for it you might as well try to mix in a few Assaults to support those Deltas.
When you attack the base of the enemy you should prioritize the following:
1. Gun Towers / Rocket Towers (the rush will be more likely to fail if your enemy manages to fully construct any)
3. Assault Factories (blue / red) - skip if they aren't built in the back of the base
The following priorities have such a low priority as your enemy can easily rebuild them with Boosts:
4. Headquarters (blue / red) - if you destroy it than you already succeeded in your rush (exception: Your enemy uses HQ Reconstruction boost).
5. Administrative Buildings
Note:
Deltas, similar to Hammers, are very mobile. Use this advantage to deal with Grenadiers if you have to.
Walls (blue / red) are known to mess with the pathfinding of Deltas and can seriously hinder your rush.
This tactic is usually easier to pull of against Confederation enemies, as they are often very reluctant to go for navy, therefore almost guaranteeing you the Best Case scenario
This tactic can also be used in 2v2 to make a tech Rush for your partner easier by distracting the enemies.