It's nice to see different opinions on the builds and elements. I've seen people saying various things about ranging from it being weak to it being one of the best support elements.
Water by itself isn't that strong, but Bubble Gems can be transform into Freeze or Shock Gems easily, so they're good source for providing these gems in a few actions. For Chapter 0 and Chapter 1, you can use Aqua Splash and Frostbite to keep making 2+ Freeze Gems on the board, then cash out later with Forward Dash or Glacial Strike. From Chapter 2 onwards, you'll have more ways to use the Freeze Gems with Armor Bonuses. You'll also have an option to use Elec with Water, which lets you make a stun-lock build with Water, Elec, then converts Shock Gems into Paralyze Gems.
I can see that it might be tough to see its strength right now in Chapter 0 and Chapter 1, but once you unlock Skill Stores in Chapter 2, it'll open up to many interesting builds.
- Punipen