You might call them bobby corks.
They come in all sorts of styles and sizes. You want a casting style. Like the cone shaped pictured. They are cone shaped to reduce air drag when casting.
Use a float stopper as pictured. The float stopper is safe to go over the rod guides. Using a float stopper means you can adjust the depth of your bait. Just ask your local tackle shop to show you how to put the stopper on the line. It is very easy...Just tell them Itsaboat from Fishing Reminder sent you hahaha.
You can also use lures with a float. The "teaser" float pictured is ideal for lures. For 50 years I called them glitter floats. But apparently they are called teaser floats. The flickering light gets the fish attention. When they come to look they find your lure. The water movement makes the lure move a little bit and looks like something nice to eat.
Ballooning is a big step up from floating but same principle. If you are using a heavier bait, like a live bait, then a balloon is usually better.
Some people will use a short length of line to attach the balloon. I strongly object to that. Tie the balloon direct to your main line. That way you can still slide the balloon up and down to adjust for depth and if the balloon burst and the tag line breaks it is not left in the water for some poor turtle to choke on !!
I have talked about it many times over the years. 90% of people cast straight over the fish they are trying to catch. In this case you are putting your bait on the bottom where the rays are. Affectively "casting" past the fish you are trying to catch. If there are rays, then above them will be sharks and above the sharks will be the target fish. Pelagic (surface hunters) will be there. The idea is you want to float your bait (or lure) at the depth (feeding zone) of the pelagics.
I usually start between 6 and 10 feet depth and go from there....A few years ago I found a very interesting spot. I posted about it at the time. I was fishing a beach gutter at Lake Bunga in Victoria. It was a strike every cast. But the feed zone was so tight, casting just 30cm (12 inches) to the side meant no strike.