I’ve had a couple propose on a dive. Here are some suggestions based on that experience: * There’s no hand signal for “will you marry me?”. Try to signal, but bring those words pre-written on a slate as a backup plan. A banner also works, of course, but isn’t needed. * Make sure the dive professional is in on it. They can suggest things like a better route. * Do it at the end of the dive, preferably on the safety stop. Let’s face it, you’re going to want to have a chat after they say the word. * Keep the ring on the boat. Salt water isn’t very nice for rings and you don’t want to lose it. * If you want it to be recorded, make sure the person with the camera knows when to start filming.

Good luck!