Ecco: Defender of the Future question

[Ecco]

I've been exploring this game, but using the level-select code, and not properly pushing through every single stage. So I'm not quite seeing all the content, though I'm seeing every stage.

The cut-scenes include Metamorphosis twice, but I'm still wondering if it happens during actual gameplay? If so, where does it happen, and what creatures can you play as?

(Unless someone tells me otherwise, I'm inclined to think that it actually only happens in cut-scenes, and not the gameplay?)

(Also, I know there are long-plays on YouTube but I don't actually want to watch someone play through the entire game lol.)

[cleeg]

You change into a fish two or three times in order to squeeze through gaps.

[Ecco]

^Is that absolutely all of the Metamorphosis? Turning into a fish? What an underused gimmick lol. And it was such a big part of Tides of Time.