I am hoping to can gather all known glitches related to the Ecco the Dolphin series and document them. It seems there is a lot of well known glitches for the Ecco series but no website to etch them in stone and confirm if they exist.
Interesting Things is an article series dedicated to documenting glitches and intentional elements in the games. If you have an Interesting thing from the Ecco series that you'd like to submit please send an email to Johnny.dealba at Gmail.com and I'll try to feature it.

To find the shortcut through Crystal Springs locate the rocks creating a barrier to the levels exit. Swim into the lowest rock until your able to pass through it to the next level.

In the level Dark Sea locate the Glyph in the lower left corner of the level that swallows barriers. Once you've used the "Eater" Glyph and entered the path directly below the Milestone Glyph, there is a path to the left. Follow it to the room with the Invincibility Glyph.
Get invincibility, swim to the top-right corner of this room (not the passageway) and swim as fast as you can (by pressing C) to the left! Basically your swimming to the top right corner to get a head start as you speed as fast as you can to the left, allowing you to pop through the wall.
You'll pop right through the wall, skipping an enormous chunk of the auto-scrolling section! I've tested this multiple times, it has worked *every* time, so it's a very easy glitch to perform.

When the Vortex Queen came to Earth she created a new race that explode when they reach the waters surface. It was never understood if this was intentional until Epicenter of DARK SEA interviewed Ed Annunziata. In the interview Ed said those particular drones were designed for the extreme pressure of the deep sea.
Source: DARK SEA - Ecco Team Interview: Ed Ettore Annunziata
Related: Interesting Things in Ecco 2: The Tides of Time - 07-30-2009