In Australia, it is completely legal to use drones for fishing. However, regulations apply to recreational drone pilots. The Australian Civil Aviation Safety Authority (CASA) regulates all aircraft in Australian airspace, including drones. A fishing drone flying off the beach is technically an aircraft, so CASA rules apply.
According to the 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. Drones weighing over 250g should not be flown closer than 5.5km from controlled airports (airpors with control towers). Drones weighing over 25kg must be approved and registered with CASA.
As drone bait deployment falls under recreational fishing, standard state fishing licenses apply. Recreational fishing licenses are required in NSW, VIC, and ACT. Other Australian states (WA, QLD, SA, NT & TAS) do not require a license, however specific protected zones such as national parks, conservation parks and marine parks prohibit fishing and drone use altogether. 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.