Flying liquid hydrogen – the 2021 update - NLR News
Aerial drone panoramic photo of the picturesque port and main village of Hydra (or Ydra) island at sunset. Hydra is a top tourist destination with neo Stock Photo - Alamy
Hydra Technologies Ehécatl - Wikipedia
Hydra - Volatus
UK Army Unveils Jet Drone 'Hydra 400' with Laser Missiles
Professional UAV - HYDRA-12 - AltiGator - measurement / agricultural / transport
DARPA's 'Hydra' would be an undersea drone carrier
Amazon.com: WowWee HydraQuad 3-in-1 Hybrid Air to Water Stunt Drone – Remote Control Toy for Kids : Toys & Games