Hi Unreal community! I want to create an underwater environment, but I’m encountering a lot of difficulties. Can you tell me wich are the settings to modify?
You can do it with a combination of a post process volume, some material and particle effects. 
e.g in this video he uses the post process volume to change the scene colour underwater: ?v=LtyXjSb1P-4
Here is a demonstration of a underwater effect: ?v=F7iK6u-w3Po -> bubble particles, post process effect (same as in the video above), I think the effects on the ground were made with a material
There is no one button underwater solution- what settings are you talking about?
General starting point I would look at Post Process Volumes, Height and Atmospheric Fog and lighting. There is a lot you can do there to sell the effect and will keep you busy for a long time.
Once you have that, I’d start looking into gameplay (gravity) implementation and finally higher end polish (particles, caustics, materials).