How These Were Made

Its a WebObject with Canvas on it. If you check it in the console you end up here...
https://www.amnvohra.com/projects/fish/story_content/WebObjects/5te71AC6ooa/index.html 
The size he uses is 1160x576..
The Canvas is called "jsi-ripple-container", so probably somewhere a Javascript ripple library called something like that that handles all.

And a bit of search... here it is... the original...
https://codepen.io/K-T/pen/Ldgdab

jQuery in fact is the only library used in this.
Every fish in fact is a geometrical calculation and draws on Canvas using this kind of code.
https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D
A function createGoldfishes( ) creates them and each instance has specific settings in code.
GOLDFISH.prototype = {
OFFSET : 30,
RIPPLE_INTERVAL : 20,
VELOCITY_LIMIT : 0.3,

In the second slide it just another SlideLayer on top of the previous one.

Kind regards,
Math