Sports Illustrated swimsuit model Marisa Miller has shared her baby bump to the world by tweeting a picture of herself underwater in a bikini to her followers on Twitter.

The former Victoria's Secret model who recently turned 34, is expecting her first child with Griffin Guess.

Along with the photo of her swimming underwater, Miller tweeted a message thanking fans for her birthday wishes. "Thanks so much for all the sweet birthday wishes! Love you all! I had the best day and spent most of it under water...."

On August 2, Miller posted another photo, tweeting ""This was a month ago at 17 weeks. My belly seems to have doubled since! Had to paddleboard to get to this cave." Her baby is due in December.

Miller and music producer Guess married in 2006.  She was previously married to Jim Miller, a lifeguard from California. The marriage lasted from 2000 to 2002. Born Marisa Lee Bertetta, she continued to use the surname Miller as she progressed in her career.

Miller appeared in every issue of Sports Illustrated Swimsuit issue from 2002 to 2008. During that time, she also worked as a model for Victoria's Secret. She also appeared in GQ, Maxim, Glamour, Cosmopolitan, and Elle.

She topped Maxim magazine's "Hot 100" for 2008 and has been dubbed the "return of the great American supermodel."

Tags: marisa miller