Hydrodashing has to my my favorite way for Sonic to go fast for several reasons, and I just wanted to share that because maybe someone else finds this kind of stuff interesting as well! To summarize, it mostly comes down to Controlls, visuals, and sound design done really well!
The controlls in hydrodashing, aside from having glitchy physics, are just perfect to me! You can go pretty fast in the hydrodash stage, but the faster you go, the less flexible the character becomes when turning! If you stop going forward, The character will slow down by alot. you can use this to quickly break but not stop fully to make a quick turn, or to slow down rather quickly but not instantly to land on small platforms without too much of a struggle! There is also a slight magnetic like automation, that slightly pushes you towards helpfull objects in a very short range, which is hardly noticable but makes a world of diffrence controllwise!
The Visuals also are very important when it comes to hydrodashing! The animation put on Sonic and Tails really makes it seem relaxed and thrilling at the same time! They are putting not alot of effort at reaching their speed, but can seem quite struggling when avoiding alot of obstacles!
But the most important thing has to be the sound design! Most Sonic games with speed have a loud, high pitched sound. I dont know exactly why they did that aside from the genesis games, I guess because it feels more powerfull.. Either way, in Hydrodashing you hear the relaxing sound of water, while going at high speeds! This is great, rather then be intense at all times, hydrodashing can feel really relaxing when nothing much is going on, but if the background sound is more tense, Hydrodashing will be as well!
Its a shame Hydrodashing is only used in this game, I feel its really underrated.. Anyways, thanks for reading to my rambling about a mostly forgotten gimmick!