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.
This means, under Florida law, that it is a sex offense - “lewd and lascivious molestation” - punishable by up to fifteen years in prison, for a sixteen year old to engage in sexual activity with a fifteen year old.
Technically speaking, under the terms of the statute, if two fifteen year olds engage in sexual activity together, they are both committing sex offenses upon each other under Florida law.
However, just because your boyfriend can't be convicted doesn't mean that your dad can't stir up trouble. You want to play adult games with sex and love but don't have any idea what you would do if you made a child. That is like telling a firebug that it is okay to whip up a batch of bathtub napalm because fires make them feel good.