Question Shader effect shows black when transparency alpha set to 0 on skybox

I'm not exactly sure how to title this (probably because I don't know the real issue.

I'm thinking it's something how the clear flags are handled but I'm not sure.

Here is the effect I have right now. I'm tracking objects and showing a glow around them as they approach the plane. It works fine if I have something behind the plane but when It's just the skybox it paints over what was there before rather than showing just the skybox behind the desired effect.


Here is the relevant shader code:

Code (CSharp):

1. Shader "Unlit/BoundaryField"
2. {
3.     Properties
4.     {
5.         _MainTex ("Texture", 2D) = "white" {}
6.         _Color ("Color", Color) = (1,1,1,1)
7.         _EffectColor ("Effect Color", Color) = (1,1,1,1)
8.         _Distance ("Max Effect Distance", float) = 1
9.         [Enum(UnityEngine.Rendering.CullMode)] _Cull("Cull", Float) = 2
10.         [Enum(UnityEngine.Rendering.BlendMode)] _SrcBlend ("Src Blend", Float) = 1
11.         [Enum(UnityEngine.Rendering.BlendMode)] _DestBlend ("Dest Blend", Float) = 0
12.     }
13.     SubShader
14.     {
15.         Tags
16.         {
17.             "RenderType"="Opaque"
18.             "RenderPipeline" = "UniversalPipeline"
19.             "Queue" = "Geometry"
20.         }
21.         Pass
22.         {
23.             LOD 100
24.          
25.             Blend [_SrcBlend] [_DestBlend]
26.             Cull [_Cull]
27.             ZWrite On
28.  
29.             HLSLPROGRAM
30.             #pragma vertex vert
31.             #pragma fragment frag
32.  
33.             #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
34.             #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/DeclareDepthTexture.hlsl"
35.  
36.             struct appdata
37.             {
38.                 float4 vertex : POSITION;
39.                 float2 uv : TEXCOORD0;
40.             };
41.  
42.             struct v2f
43.             {
44.                 float2 uv : TEXCOORD0;
45.                 float4 vertex : SV_POSITION;
46.             };
47.  
48.             sampler2D _MainTex;
49.             float4 _MainTex_ST;
50.             float _Distance;
51.             float4 _Color;
52.             float4 _EffectColor;
53.             vector _Positions[1000];
54.             float _ArraySize;
55.  
56.             v2f vert(appdata v)
57.             {
58.                 v2f o;
59.                 o.vertex = TransformObjectToHClip(v.vertex.xyz);
60.                 o.uv = TRANSFORM_TEX(v.uv, _MainTex);
61.                 return o;
62.             }
63.  
64.             half4 frag(v2f i) : SV_Target
65.             {
66.                 float2 uv = i.vertex.xy / _ScaledScreenParams.xy;
67.                 #if UNITY_REVERSED_Z
68.                 real depth = SampleSceneDepth(uv);
69.                 #else
70.                     real depth = lerp(UNITY_NEAR_CLIP_VALUE, 1, SampleSceneDepth(uv));
71.                 #endif
72.  
73.                 float3 pixelWorldPos = ComputeWorldSpacePosition(uv, depth, UNITY_MATRIX_I_VP);
74.  
75.                 float4 color = tex2D(_MainTex, i.uv) * _Color;
76.  
77.                 for (int iObject = 0; iObject < _ArraySize; iObject++)
78.                 {
79.                     vector position = _Positions[iObject];
80.                     float dist = distance(pixelWorldPos.xyz, position.xyz);
81.  
82.                     if (dist <= _Distance)
83.                     {
84.                         color = lerp(color, _EffectColor, 1 -(dist / _Distance));
85.                     }
86.                 }
87.  
88.                 return color;
89.             }
90.             ENDHLSL
91.         }
92.     }
93. }