Florida Law requirements regarding the Diver Down Flag & Buoy
The following regulations apply whenever someone is wholly or partially submerged and is using a face mask and snorkel or underwater breathing apparatus. A divers-down warning device may be a divers-down flag, buoy, or other similar warning device. These devices are designed for, and used by, divers and dive vessels as a way to notify nearby boaters that divers are in the water in the immediate area. The device must be displayed prominently when in use. The divers-down warning device must meet the following requirements.

• The divers-down warning device must contain a divers-down symbol. The symbol is a red rectangle or square with a white diagonal stripe. If the symbol is a rectangle, the length may not be less than the height or more than 25% longer than the height. The width of the stripe must be 25% of the height of the symbol. If multiple stripes are displayed, all of the stripes must be oriented in the same direction.
• The size of the divers-down symbol depends on whether the divers-down warning device is displayed from the water or from a vessel. On the water, the divers-down symbol must be at least 12 x 12 inches in size. On a vessel, the symbol must be at least 20 x 24 inches in size.
• When displayed on a boat, the divers-down warning device also must be displayed at the highest point of the vessel so that its visibility is not obstructed in any direction.
• If the divers-down warning device is a flag, the divers-down symbol must be on each face and have a wire stiffener or be otherwise constructed to ensure it remains fully unfurled  and extended, even when there is no wind or breeze.
• If the divers-down symbol is a buoy, the buoy must have three or four sides with the divers-down symbol displayed on each of the flat sides. The buoy must be prominently visible on the water’s surface and can’t displayed on the vessel.
• Boaters must make reasonable efforts to stay at least 300 feet away from divers-down warning devices in open water and at least 100 feet away in rivers, inlets, or navigation channels. Boaters approaching divers-down warning devices closer than 300 feet in open water and 100 feet in rivers, inlets, or navigation channels must slow down to idle speed.
• Divers-must make a reasonable effort to stay within 100 feet of a divers-down flag or a buoy within rivers, inlets, or navigation channels and within 300 feet on open water.
• A divers-down warning device may not be displayed when divers are out of the water.