Don't get too close. VPS will not work right over water so you want to keep a good distance, 10 or 15 feet minimum I would say. It also wouldn't be a bad idea to have a plan in place if it goes in. Some people have rigged pool noodles to the legs to provide floatation and I would also recommend getterback, technically getterback was made for fishing poles but it works for drones too, it just attaches to the leg and if the drone sinks it automatically activates (chemically) just like an inflatable life raft on a ship once it reaches about 10 feet. Instead of a raft though it launches a buoy attached to the drone with 100 feet of 10 pound test fishing line so as long as it is less than 100 feet down you can just grab the buoy and pull it back to the surface. Ofcourse that assumes you are able to reach it, if your planning to fly beyond an area where you can wade in or swim out to it you will need a boat, carrying an automatically inflating boat with you with some ores or an electric motor or something wouldn't be a bad idea.
Be weary of seagulls, they like to attack drones because they think they are rival seagulls. Be mindful of interference to the compasses from dock poles, boats, and bridges. Watch for pressure changes that could throw off your barometer. Make sure your home point is a safe spot on land above the high water line that you can get to and you don't fly out of range, if you can't than set the failsafe to hover instead of return to home. Try to keep it in view, if it goes into the water without you seeing where you will likely never be able to find it as trackers likely will not work underwater unless you get lucky and see it floating on the pool noodles or see the getterback bouy or the water is shallow enough to see it.
