Man vanishing into bathtub

I’ve been looking for this movie for most of my life.

I was quite young when I saw it, so the movie must have been made before 2000.

This is the scene I remember.

A man saw his reflection in a humongous tub of water. He touched it with his finger.

It created ripples. In them he realised how the lightest touch can alter your perception of yourself and the reality of the ways others view you.

Upon a closer look he detected something beneath the surface of the water. He stuck his whole arm in to feel the depth of this tub. His hand just continued in.

Gradually he went deeper in. All in order to physically feel were the bottom was. He needed to feel the bottom for his own sanity’s sake. But there was no bottom to be found.

So in the end he dove in. The next scene is him beneath the surface. In this magical world of light and sea creatures.

Any clue about what this movie is would be greatly appreciated, I wish I remembered more.