Michelle Casillas is in the third year of her second stint as the diving coach at UC San Diego in 2012-13. She previously served in the same capacity for two seasons from September 2004 to March 2006.

Both the UCSD men's and women's squads won their fourth consecutive Pacific Collegiate Swimming & Diving Conference (PCSC) titles in 2012, before they duplicated their second- and third-place showings, respectively, at the NCAA Division II Swimming & Diving Championships in Mansfield, Texas. Casillas qualified three men's divers to the NCAA meet, after Tyler Runsten had won a third straight PCSC crown in the three-meter event. She was named PCSC Men's Diving Coach of the Year.

In 2010-11, Casillas coached Runsten, then a sophomore, to a second-place finish on the three-meter springboard at the 2011 NCAA Championships in San Antonio, Texas. He also took fifth in the one-meter.

With Runsten winning from three meters at the 2011 PCSC meet, then-freshman Luke Calkins placed third and Patrick Cohen was seventh. In the one-meter event, Runsten took second while Calkins was fourth and Cohen was sixth.

Since Casillas has been with the Tritons, UCSD produced the first two NCAA All-American divers since the program moved up to Division II for the 2000-01 season.

Casillas served as a master trainer/manager at Guaranteed Fitness, a health coach at StayWell Health Management, a gym director at The Little Gym and a personal trainer at Snap Fitness prior to returning to UCSD. Certified by the National Strength and Conditioning Association (NSCA) as a Strength and Conditioning Specialist (CSCS), Casillas has nearly eight years of training and coaching experience.

Casillas competed as a varsity diver for the University of Nevada from August 1997 to January 2000, earning All-Big West Conference honors four times. She then joined the varsity diving team at Florida State University, where she competed from August 2000 to March 2002 and was a three-time All-Atlantic Coast Conference performer. She graduated from Florida State in 2002 with a bachelor's degree in sports management.

Casillas resides in Temecula with her husband and two children.