This drone can send an attachement underwater for investigation and repair. Inital application looks to be for offshore wind-farms. Via DesignBoom:

japanese telecommunications operator KDDI, commercial drone manufacturer prodrone, and underwater robotics firm QYSEA have collaborated to create the world’s first commercial drone that can both fly in the air and swim underwater. first unveiled during a flight showcase at the hakkeijima sea paradise amusement park in yokohama, japan, the ‘sea-air integrated drone’ intends to modernize offshore and marine operations with its ingenious capabilities, high efficiency, and minimized manpower requirements.

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Welcome to drone day on the Adafruit blog. Every Monday we deliver the latest news, products and more from the Unmanned Aerial Vehicles (UAV), quadcopter and drone communities. Drones can be used for video & photography (dronies), civil applications, policing, farming, firefighting, military and non-military security work, such as surveillance of pipelines. Previous posts can be found via the #drone tag and our drone / UAV categories.