reflectionColor.rgb does at some pixels have large negative values < -50 which cases the SSR blur pass to create big artifacts:
The workaround is to clamp the reflection color to 0-1 but the root cause should be investigated. From investigating the UV coordinates used for the sampling seems to be in range and also the output texture from the water job does not contain these large negative values so where they are introduced into the texture is unknown.
In data\shaders\ssr\ssr.frag when sampling at the SSR hitPixel UV coordinate with
reflectionColor = vec4((texture(_MainTex, hitPixel)).rgb, alpha);
reflectionColor.rgb does at some pixels have large negative values < -50 which cases the SSR blur pass to create big artifacts:
The workaround is to clamp the reflection color to 0-1 but the root cause should be investigated. From investigating the UV coordinates used for the sampling seems to be in range and also the output texture from the water job does not contain these large negative values so where they are introduced into the texture is unknown.