Custom-Fish.shader

Shader "Custom/Fish" {
Properties {
    _Color ("Main Color", Color) = (1,1,1,1)
    _SpecColor ("Specular Color", Color) = (0.5, 0.5, 0.5, 1)
    [PowerSlider(5.0)] _Shininess ("Shininess", Range (0.03, 1)) = 0.078125
    _Clipping ("Clipping", float) = 1
    _MainTex ("Base (RGB) Gloss (A)", 2D) = "white" {}
    _BumpMap ("Normalmap", 2D) = "bump" {}
    _WiggleAmp ("Wiggle Amplitude", float) = 1
    _WigglePeriod("Wiggle Period", float) = 1
    _FishDistance("How far the fish hath traveled", float) = 0
}

CGINCLUDE
sampler2D _MainTex;
sampler2D _BumpMap;
fixed4 _Color;
half _Shininess;
float _WiggleAmp;
float _WigglePeriod;
float _FishDistance;
float _Clipping;
struct Input {
    float2 uv_MainTex;
    float2 uv_BumpMap;
};

void vert(inout appdata_full v) {
	// add the normal to the vertex
    float3 localpos = v.vertex;
    float3 worldpos = mul(unity_ObjectToWorld, v.vertex).xyz;

	v.vertex.x += sin((_FishDistance + v.vertex.z) * _WigglePeriod) * _WiggleAmp;
}

void surf (Input i, inout SurfaceOutputStandard o) {

    fixed4 tex = tex2D(_MainTex, i.uv_MainTex);
    o.Albedo = tex.rgb * _Color.rgb;
    clip(tex.a + -_Clipping);
    o.Alpha = tex.a * _Color.a;
    o.Smoothness = _Shininess;
    o.Normal = UnpackNormal(tex2D(_BumpMap, i.uv_BumpMap));
}
ENDCG

SubShader {
    Tags { "RenderType"="Opaque"
            "Queue"="Geometry"
        }
    LOD 400

    CGPROGRAM
    #pragma surface surf Standard fullforwardshadows vertex:vert addshadow
    #pragma target 3.0
    ENDCG
}

SubShader {
    Tags { "RenderType"="Opaque" 
            "Queue"="Geometry"
        }
    LOD 400

    CGPROGRAM
    #pragma surface surf Standard fullforwardshadows vertex:vert addshadow
    ENDCG
}

FallBack "Legacy Shaders/Specular"
}

FishWiggle.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class FishWiggle : MonoBehaviour
{
    public AnimationCurve WiggleAmplitude;
    public float DistanceScalar = 1;
    public float BaseSpeed = 0f;

    private Renderer fishRenderer;
    private float fishDistance = 0;
    private Vector3 lastPosition = Vector3.zero;
    private float wiggleAmplitude = 0;
    private float wiggleLerp = 2f;

    // Start is called before the first frame update
    void Start()
    {
        lastPosition = transform.position;
        fishRenderer = GetComponentInChildren<Renderer>();      
    }

    // Update is called once per frame
    void Update()
    {
        var distance = Vector3.Distance(transform.position, lastPosition);
        lastPosition = transform.position;
        fishDistance += distance;
        fishDistance += BaseSpeed * Time.deltaTime;
        wiggleAmplitude = Mathf.Lerp(wiggleAmplitude, WiggleAmplitude.Evaluate(distance / Time.deltaTime), Time.deltaTime * wiggleLerp);

        if(float.IsNaN(wiggleAmplitude))
        {
            wiggleAmplitude = 0;
        }

        fishRenderer.material.SetFloat("_FishDistance", fishDistance * DistanceScalar);
        fishRenderer.material.SetFloat("_WiggleAmp", wiggleAmplitude);
    }
}