I’d like to comment on the change of the underwater use of rocket boots for the Engineer.
On the Elementalist, underwater skill 3 (I believe) under Air Attunement shoots a bubble and teleports the player wherever the bubble lands. If you aim to the sky while underwater, it can teleport you somewhere out of the water enabling the character to reach unintended places.
For example: In Raid of Capricorn, I can use this skill to reach any of the ledges above the underwater capture point and thus, use land skills that damage players underwater. I’m sure other classes have similar teleporting skills that can shoot a player into the sky from underwater.
If the change to rocket boots was for a reason similar to which I just described, you might want to look into those other underwater skills that teleport players.