Flying over water is no big deal. However, if there is no wind, then all of DJI drones can struggle reading the 'terrain'. They become confused, and begin to lower themselves. So be sure to watch that it doesn't lower itself while hovering. If you are not going too slow, or hovering you should be fine. Still, it's best to stay at least 10 feet above water for the first few flights, or more
For shooting video, you want to follow the basic rules of photography, and point the drone camera away from the sun, or at most 90 degrees to the sun.
Many people use manual mode instead of auto mode, and I do too.
For white balance, don't use automatic white balance (AWB). Instead, I use custom at 5600 Kelvin (you'll see Custom in the app with a slider) Some people select "Sunny", or "Cloudy" each are programs to adjust the Kelvin temperature based on the amount of light. If it's cloudy the program adjusts Kelvin toward 3200 to "warm" the image up. And, if it's sunny, the program adjusts Kelvin toward 5600 to cool it down. Your best bet is to select Sunny, or Cloudy until you are confident Once confident, play with the Kelvin slider and look at the monitor to get a look that you like.
Many people select log profiles, or D-cinelike for a flat image with a lot of dynamic range. They do this to use a computer for color correction, and color grading. If you don't want to do the computer work, then select a pre-packaged color profile you like.
A lot of people buy ND (neutral density), or polarizing filters to lower the shutter speed toward twice the frame rate, such as 24FPS, 30FPS, or 60FPS, etc... I have purchased them, but don't use them. It's all about motion blur, but I fly too high (less that 250 feet) to capture motion blur.
If you are going to color correct for white balance, or color grade for cinematic looks, be sure your computer is strong enough to handle 4K video. If not, then film in 2.7K, or 1080p, or whatever your computer can process easily. It's frustrating to film in 4K to discover your computer can't process 4K video.