Basically some mathematical algorithms

Shader part:

shader "unlit/2d-ocean"
{
 properties
 {
 _maintex ("texture", 2d)="white" {}
 _suncolor ("suncolor", color)=(1,1,1,1)
 _sunroundcolor ("sunroundcolor", color)=(1,0,0,1)
 _wavecolor1 ("wavecolor1", color)=(1,1,1,1)
 _wavecolor2 ("wavecolor2", color)=(1,1,1,1)
 _wavecolor3 ("wavecolor3", color)=(1,1,1,1)
 _wavecolor4 ("wavecolor4", color)=(1,1,1,1)
 _wavecolor5 ("wavecolor5", color)=(1,1,1,1)
 _skycolor ("skycolor", color)=(0,1,0,1)
  _cloudpos1 ("cloudpos1", vector)=(0,0,0,0)
 _cloudpos2 ("cloudpos2", vector)=(0,0,0,0)
 _cloudpos3 ("cloudpos3", vector)=(0,0,0,0)
 _cloudpos4 ("cloudpos4", vector)=(0,0,0,0)
 _cloudpos5 ("cloudpos5", vector)=(0,0,0,0)
 _wavefactor1 ("wavefactor1", vector)=(0,0,0,0)
 _wavefactor2 ("wavefactor2", vector)=(0,0,0,0)
 _wavefactor3 ("wavefactor3", vector)=(0,0,0,0)
 _wavefactor4 ("wavefactor4", vector)=(0,0,0,0)
 _wavefactor5 ("wavefactor5", vector)=(0,0,0,0)
 _sunpos ("sunpos", vector)=(0,0,0,0)
 _sunroundfactor ("sunroundfactor", range (0.0,2.0))=0.1
 _sunsize ("sunsize", range (0.0,1.0))=1.0
 }
 subshader
 {
 tags {"rendertype"="transparent"}
 lod 100
 blend srcalpha oneminussrcalpha
 pass
 {
 cgprogram
 #pragma vertex vert
 #pragma fragment frag
 #include "unitycg.cginc"
 struct appdata
 {
 float4 vertex:position;
 float2 uv:texcoord0;
 };
 struct v2f
 {
 float2 uv:texcoord0;
 float4 vertex:sv_position;
 };
 sampler2d _maintex;
 float4 _maintex_st;
 float4 _cloudpos1;
 float4 _cloudpos2;
 float4 _cloudpos3;
 float4 _cloudpos4;
 float4 _cloudpos5;
 float4 _wavecolor1;
 float4 _wavecolor2;
 float4 _wavecolor3;
 float4 _wavecolor4;
 float4 _wavecolor5;
 float4 _wavefactor1;
 float4 _wavefactor2;
 float4 _wavefactor3;
 float4 _wavefactor4;
 float4 _wavefactor5;
 float4 _suncolor;
 float4 _sunroundcolor;
 float4 _sunpos;
 float _sunroundfactor;
 float _sunsize;
 float4 _skycolor;
 //Draw a single circle (uv, position, size, anti-aliasing)
 float4 circle (float2 uv, float2 center, float size, float blur) {
 uv=uv-center;
 uv=uv/size;
 float len ​​= length (uv);
 //Length greater than a radius unit transparency is 0, less than transparency is 1
 float val=smoothstep (1.0,1.0-blur, len);
 return float4 (1, 1, 1, val);
 }
 //Draw a single cloud
 float4 drawcloud (float2 uv, float2 center, float size) {
 uv=uv-center;
 uv=uv/size;
 float4 col=circle (uv, float2 (0.0, 0.0), 0.2, 1);
 //Cut off the unwanted part of the circle
 col=col * smoothstep (-0.1, -0.1 + 0.01, uv.y);
 //The circle is placed in different positions to form a cloud
 col +=circle (uv, float2 (0.15, -0.05), 0.1, 1);
 col +=circle (uv, float2 (0.0, -0.1), 0.11, 1);
 col +=circle (uv, float2 (-0.15, -0.1), 0.1, 1);
 col +=circle (uv, float2 (-0.3, -0.08), 0.1, 1);
 col +=circle (uv, float2 (-0.2, 0.0), 0.15, 1);
 return col;
 }
 //Draw a plural cloud
 float4 drawclouds (float2 uv) {
 uv.x +=0.03 * _time.y;
 //Make left and right continuous
 uv.x=frac (uv.x + 0.5)-0.5;
 float4 col=drawcloud (uv, _cloudpos1.xy, 0.1);
 col +=drawcloud (uv, _cloudpos2.xy, 0.12);
 col +=drawcloud (uv, _cloudpos3.xy, 0.14);
 col +=drawcloud (uv, _cloudpos4.xy, 0.16);
 col +=drawcloud (uv, _cloudpos5.xy, 0.18);
 return col;
 }
 //Draw the sun halo
 float4 drawsuncircle (float2 uv, float2 center, float size) {
 uv=uv-center;
 uv=uv/size;
 //atan2 returns the angle between the point (x, y) and the x axis,Range (-π, π)
 //Get the θ angle of polar coordinates
 float degree=atan2 (uv.y, uv.x) + _time.y * -0.1;
 //The distance of the uv vector from the center
 //Get the square of r=x2 + y2 in polar coordinates
 float len ​​= length (uv);
 //According to the polar coordinate rose line:r (θ)=a * sin (kθ)
 //Find r;a is the diffusion amplitude,k is the number of petals * 0.5
 float r=0.3 * abs (sin (degree * 5.0));
 //Draw petals
 //Retain all pixels whose r value is less than the distance to the center
 float sunround=smoothstep (r + 0.1 + _sunroundfactor, r + _sunroundfactor, len);
 return float4 (1,1,1, sunround) * _ sunroundcolor;
 }
 //Draw waves (parameters:uv, frequency, amplitude, overall height,Moving speed)
 float4 drawwave (float2 uv, float wavefrequency, float waveamplitude, float waveheight, float speed) {
 uv.x +=speed * _time.y;
 uv.y +=sin (_time.y + waveheight) * 0.02;
 //The transparency of uv.y greater than the sin function is 0, and the transparency of the less than 1 is 1.
 float val=uv.y-sin (uv.x * wavefrequency) * waveamplitude-waveheight;
 val=smoothstep (0.001,0.0, val);
 return float4 (1, 1, 1, val);
 }
 //Draw background
 float4 drawbackground (float2 uv) {
 float4 val=lerp (float4 (1,1,1,1), _skycolor, uv.y);
 return val;
 }
 //Mixed layer (b is foreground, a is background)
 float4 lerpimages (float4 a, float4 b) {
 return float4 (lerp (a, b, b.a) .rgb, a.a + b.a);
 }
 v2f vert (appdata v)
 {
 v2f o;
 o.vertex=unityobjecttoclippos (v.vertex);
 o.uv=transform_tex (v.uv, _maintex);
 return o;
 }
 float4 frag (v2f i):sv_target
 {
 //Sun Center
 float4 suncorecolor=circle (i.uv, _sunpos.xy, _sunsize, 0.05) * _ suncolor;
 //Sun Halo
 float4 sunaroundcolor=drawsuncircle (i.uv, _sunpos.xy, _sunsize);
 //cloud
 float4 cloudscolor=drawclouds (i.uv);
 //wave
 float4 wave1=drawwave (i.uv, _wavefactor1.x, _wavefactor1.y, _wavefactor1.z, _wavefactor1.w) * _ wavecolor1;
 float4 wave2=drawwave (i.uv, _wavefactor2.x, _wavefactor2.y, _wavefactor2.z, _wavefactor2.w) * _ wavecolor2;
 float4 wave3=drawwave (i.uv, _wavefactor3.x, _wavefactor3.y, _wavefactor3.z, _wavefactor3.w) * _ wavecolor3;
 float4 wave4=drawwave (i.uv, _wavefactor4.x, _wavefactor4.y, _wavefactor4.z, _wavefactor4.w) * _ wavecolor4;
 float4 wave5=drawwave (i.uv, _wavefactor5.x, _wavefactor5.y, _wavefactor5.z, _wavefactor5.w) * _ wavecolor5;
 //background
 float4 backgroundcolor=drawbackground (i.uv);
 //Layer overlay
 float4 finalcolor=lerpimages (backgroundcolor, sunaroundcolor);
 finalcolor=lerpimages (finalcolor, suncorecolor);
 finalcolor=lerpimages (finalcolor, wave1);
 finalcolor=lerpimages (finalcolor, wave2);
 finalcolor=lerpimages (finalcolor, wave3);
 finalcolor=lerpimages (finalcolor, wave4);
 finalcolor=lerpimages (finalcolor, wave5);
 finalcolor=lerpimages (finalcolor, cloudscolor);
 return finalcolor;
 }
 endcg
 }
 }
}