To see a Hydra in your fantasy means a gigantic impediment that is remaining in your way toward your objectives. Maybe the fantasy is attempting to let you know that you have to "utilize your head". On the other hand, the fantasy symbolizes resurrection, recovery and ripeness.

To see a hydra in your dream signifies a huge obstacle that is standing in your way toward your goals. Perhaps the dream is trying to tell you that you need to "use your head". Alternatively, the dream symbolizes rebirth, regeneration and fertility.