Published: Jul 24, 2014 10:09 PM EDT
Updated: Jul 25, 2014 12:04 AM EDT

COLLIER COUNTY, Fla.- Surrounded by family on a boat in the Florida Keys, then with quick wave to the camera, Naples man Alex Montgomery and his girlfriend Lauren Schuhle head deep underwater for the dive of their lives.

"She had no idea what was going on," said Alex Montgomery.

That's because Montgomery planned an elaborate marriage proposal underwater.

"The treasure chest and the cards that were there the banner and everything we made them 4 days before I actually proposed."

He and his family hid a treasure chest. Inside, a special message for Schuhle. Her dad recording it all, which has become a YouTube sensation.

"We'll take the gopro with us if we see something cool down there so we can tape it," said Schuhle.

The whole thing almost didn't happen. At one point, Alex realized he couldn't find the treasure chest out there in the water and he was running out of time and air.

"I told her to stay down and I surfaced and I was waving my hands to my dad asking him where was it from and he was pointing way out in the distance. I'm starting to run out of air at this point."

Just in time they found the treasure chest. Inside, a photo flip book and a banner with the big question, "Will you marry me?" The ring hidded in his special vest underwater.

"Tied to me with 200 pound plus fishing line."

"All I wanted to do was actually say yes so I tried to nod my head as fast as I could. It was beyond anything I could have dreamed," said Schuhle.