Question How to achieve bloom convolution

I am hoping to achieve a bloom effect other than the typical Gaussian convolution kernel that Unity uses by default. Rather, I want to achieve a "cross" or "plus" convolution, although that may not be the proper name.

A visual example can be seen in the water of this "Mario 3D world" course shown here:

If you pause the video and cycle through the frames with < > keys, you will see that the star-shaped glare on the water is always generated at a point on the screen where the specular component of water is very bright. This is what leads me to think this is achieved by altering the bloom image effect. The only other way I can think of applying that glare to the correct "bright points" on the screen would be to use a compute shader, although I did not think that the Switch supported compute shaders.

Can anyone offer any direction or insight into how to achieve this type of bloom effect in Unity? (Other than downloading an asset, since I would not learn anything).

Thank you!