Very bright metallic sphere appeared out of nowhere, traveled for 3 to 5 seconds and just disappeared.

I was kiteboarding at the Skyway Bridge. I stopped on a sandbar to adjust my kite. As I looked up, I noticed a very very bright metallic sphere that appeared out of nowhere and traveled for 3 to 5 seconds and then just disappeared. It was a cloud free, clear morning. The sphere was almost directly overhead. It was definitely round. You could see it plain as day. There is an Airforce Base close to the area, so I have seen multiple aircraft flying around. This was definitely not an airplane or the sun reflecting off a plane. It looked like shiny mercury in the shape of a sphere that was unbelievably bright. It was very high in the atmosphere, nowhere near where normal aircraft fly. It just appeared out of the clear blue cloudless sky and then just disappeared.