This is a gift for  Marillon954 birthday that also explain a bit more about the Elemntal Guardians' powers.

Their level of power is directly influenced by the quantity of their respective element that surrounds them; for example a Guardan of Water can have his powers severely limited when he is in a desertic area with little water but if he can be in contact with a major source of water like the ocean his power are greatly amplified.
Also all the guardians share the growing abilities as a sort of basic power.

In the pic you see Marillon in Water Guardian form (a giant otter). Hmm looks like a fishing boat is coming by... that would mean snack during bathtime!