how do u use water bomb?

[JoonKimDDS]

I bought a water bomb and about to enter the 3rd temple under the water.
I see a rock and I know that there is a temple behind it.

I set a bomb to one of the button but i can't use it under the water just like I can't use other weapons under the water.

How do i set the bomb under the water???

 

[JoonKimDDS]

nvm, forgot about boots