In Australia, it is completely legal to use drones for fishing. However, there are some general drone regulations you must comply with. According to The Australian Civil Aviation Safety Authority (CASA) guidelines, drones must be flown within a visual line of sight and cannot be flown over or near people. The flight altitude must not be higher than 120 metres above ground level.
In almost all Australian national parks, conservation parks and some marine parks, drone use is prohibited for all recreational activities, including fishing. Flying drones in prohibited areas can result in fines and other penalties.
It's important you know the laws surrounding the use of your fishing drone. Most countries have regulations regarding where and when you can fly your craft, and some places allow you to use yours freely, while others require you to get a license, register your craft, and adhere to other requirements.
You should always check local regulations before using a drone for fishing.