How do you do that you ask? well its simpler than using CSGOs Betas.

Just open your game, go to settings > game.
Then on the first section you will find the setting "Install Counter-Strike Workshop Tools", let this option on. Now you can shut the game down.





After this your steam will automaticly download the CS2 Editor.

Once its fully downloaded head up to CS2, click play and it will open a window for you to select which application you want to use. Select CS2 Editior and now just follow the next section.

All you need to do is create an Addon > Name it as you pleased > Click the Launch Tools Button.

It will open the game as a engine tester for you to test your maps (no you can not play MM on it).
Along with the game you will also find a new window called "Asset Browser", from it you will only need to launch the Map Editor.

It is reachable on the right side of the top bar with the name "Tool" and then "Hammer (Map Editor)"




Reaching on the left side on the top bar the button "File" > New.

Please make sure to select the Block Option on the Tool Properties.
















Selecting the Box Tool and then hovering to the scene of your map with the Left Button of the mouse pressed you can drag it and form a block on the map.








After releasing the Left Button of the mouse it will create a block!










Now leaving the block selected on your scene, you can go to the Active Material Tool and click on Browse so it can open a window for you to search and select the Water Texture.

(if you, perhaps accidently, deselect the block you can just use the shortcut SHIFT+S and click on the block again)











Once you clicked on "Browse" and the new window appeared, you can now go to the search bar and type "water" and then hit Enter on your keyboard to confirm the search.

After that, a few water textures will be shown for you to select one, select one which pleasures your eyes.










Now, as the final step of this guide, you will need to find the "Object Properties" Tool so you can change just one Property for your water to be really water.










Press the Button "Tie Selected Meshes to Entity" and type on the Class search bar "func_water" and hit Enter to confirm.