Waterfiend is notable for its high rate of crimson charm drop, which is extremely useful for summoning. Also, duradel and lapalok might give you waterfiends as task.

Other than these 2 reasons, there should not be any reasons to hunt them, considering that they do not give runescape gold.

There are 2 places to hunt waterfiends. One is chaos tunnel, which requires the quest what lies below to be complete and the chase of surok to be started. There is also the ancient carvebs which required completion of certain parts of barbarian training to have access to. If I am not wrong, attempting the pyre ship barbarian training will give access to the ancient carvans.

Alright, so there are 2 places, where do you go to? It is simple, the ancient carvens.

Below is how you can use runescape money to reach the ancient carvens in runescape

1.       The smartest and most vienent way would be using a game necklace( which cost no more than 1.2k in the Ge for 8 charges). Rub the necklace and teleport to the barbarian outpost. Once you reached there, run south till you reach a whirlpool. Dive in and there you are.

2.       For some reason, you do not want to use the games necklace, you can teleport to ranging guide by using a combat bracelet and run northeast. You will see a whirlpool. Dive in.

3.       you can also use a skill necklace and teleport to fishing guild and run northeast till you reach a whirlpool. Again, dive in.

4.       lastly, you can walk from whenever you are till you reach the whirlpool and dive in.