The ocean, lakes and ponds are all flat surfaces. What sells them as water is a shader — a small program that runs on the graphics card and decides the colour and shape of every pixel of the surface as it’s drawn. Four effects do most of the work, and none of them are expensive.
Moving waves
A still surface looks like glass, not water. The shader gives the surface a rolling shape by adding several sine waves together and shifting them over time. Each wave is a simple ripple; a few of them at different sizes and directions, summed, make an irregular swell that never quite repeats. Because it’s driven by the clock, it animates.
float h = 0.0;
h += sin(p.x * 1.0 + t * 1.1) * 0.6;
h += sin(p.y * 1.3 - t * 0.9) * 0.5;
h += sin((p.x + p.y) * 0.7 + t * 0.7) * 0.4;
// ...a few more, then push the surface up by hThe same wave field is reused at a smaller scale to wrinkle the surface for fine sparkle, without adding any actual geometry — the wrinkles only affect how light bounces, not the shape.
Colour by depth
Real water is lighter where it’s shallow and darker where it’s deep. The shader works out the water’s depth at each pixel by comparing the distance to the water surface with the distance to the terrain behind it (the engine provides that behind-the-surface distance). A small gap means shallow water; a large gap means deep. The colour fades from a light shade in the shallows to a dark one in the depths based on that gap. This is what gives shorelines their gradient and makes the water read as a volume rather than a flat sheet.
Foam at the shoreline
Where water meets land — where that depth is very small — the shader mixes in white foam. A clean white band would look fake, so the foam edge is broken up using the same wave field, giving it a ragged, shifting line that looks like surf.
Reflections at a glancing angle
Look straight down into water and you see into it; look across it at a low angle and it turns mirror-like and bright. That angle-dependent effect is called fresnel, and it’s a big part of why water looks like water. The shader computes how grazing the viewing angle is and blends in a brighter sky tint as the angle gets shallower, and makes the surface smoother (more mirror-like) there too. The engine’s screen-space reflections then paint nearby scenery onto that surface.
Put together — animated waves, depth colouring, broken-up foam, and a fresnel sky tint — a plain flat plane reads convincingly as water. Each generated world feeds its own colours and wave settings in, so one world’s sea can be a calm teal and another’s a deep storm-grey.
The same shader, with gentler waves, is reused for lakes and ponds. Next we leave the landscape behind and start adding life, beginning with birds built out of boxes.