How do you get the hydra's scale on mythology island?

1. You go to Poseidon's realm then go in the water and dive down where it says DIVE. You have to go down to the bottom of the sea then you will see the cave.

2. You will see this 5-headed monster to defeat the monster: when one of the heads try to get you jump on the head. Once you defeated the monster go where the body's are then you will see the scale. After you get the scale, swim back to the shore. VOILA