Here is an example of a basic water shader for Unity

Shader "Custom/Water" {
    Properties {
        _MainTex ("Water Texture", 2D) = "white" {}
        _BumpMap ("Normal Map", 2D) = "bump" {}
        _ReflectionTex ("Reflection Texture", 2D) = "white" {}
        _RefractionTex ("Refraction Texture", 2D) = "white" {}
        _WaterColor ("Water Color", Color) = (0.1, 0.3, 0.5, 1.0)
        _Specular ("Specular", Range(0, 1)) = 0.5
        _Shininess ("Shininess", Range(0, 1)) = 0.07
        _WaveSpeed ("Wave Speed", Range(0, 10)) = 1
        _WaveSize ("Wave Size", Range(0, 1)) = 0.03
    }

    SubShader {
        Tags {"Queue"="Transparent"}
        LOD 200

        CGPROGRAM
        #pragma surface surf Lambert

        sampler2D _MainTex;
        sampler2D _BumpMap;
        sampler2D _ReflectionTex;
        sampler2D _RefractionTex;
        fixed4 _WaterColor;
        float _Specular;
        float _Shininess;
        float _WaveSpeed;
        float _WaveSize;

        struct Input {
            float2 uv_MainTex;
            float2 uv_BumpMap;
            float3 viewDir;
        };

        void surf (Input IN, inout SurfaceOutput o) {
            fixed4 tex = tex2D (_MainTex, IN.uv_MainTex);
            o.Albedo = tex.rgb * _WaterColor.rgb;
            o.Alpha = tex.a;
            o.Normal = UnpackNormal(tex2D(_BumpMap, IN.uv_BumpMap));
            o.Specular = _Specular;
            o.Gloss = _Shininess;
            o.Emission = tex.rgb * _WaterColor.rgb;
            o.Reflection = texCUBE(_ReflectionTex, IN.viewDir).rgb;
            o.Refraction = texCUBE(_RefractionTex, IN.viewDir).rgb;
        }
        ENDCG
    }
    FallBack "Diffuse"
}