Our Family

Come meet the family!

John Sims ~ Instructor #CD11274

Owner & Course Director

Contact:  john@scubastuff.com

Our Director of Training and Education, John was first certified to dive in the late 1970’s. He started teaching diving in the late 80’s. As he starts his 31st year of teaching scuba diving, John is proud to say this is all he does. It isn’t a “part-time” gig, but a full-time love affair with teaching Scuba Diving. As one of the very few certified active Course Directors in Southern California, he is able to teach divers to become both scuba instructors and instructors of instructors (Instructor Trainer). He is the “old guy” with a youthful spirit and a love of teaching diving that is both calming and exciting at the same time. A little different, but very cool.



Debbie Sims ~ Instructor #15994

Owner & Equipment Guru

Contact: debbie@scubastuff.com

While most everyone that visits knows that Debbie is married to Big John, what they are often surprised to learn, is that she has been in the industry longer than he. Debbie has been rebuilding regulators and working on dive equipment since 1982. You know you have somebody special on your team when the manufacturers call you to help diagnose a problem. That actually happens. Debbie is a little old school. She usually doesn’t tell you your equipment is too old and you need a new one, unless that is the ONLY option. Debbie still cleans and polishes all the regulators. The BCD’s are meticulously cleaned. Even the Velcro is brought back to as good a condition as possible. Every piece of equipment sold or serviced comes with Debbie’s thoughts on how to keep it functioning for years to come. Debbie doesn’t “make due”. Debbie makes it right. In the 25 years at the shop Debbie has had 3 complaints. All exactly the same. She restored a product to “factory new” and the customer complained because it breathed too easy. Sometime you forget how well this equipment is supposed to operate. Don’t ask her how much something will cost. She will only tell you what her labor charge will be. Even if it takes her several extra hours, her labor doesn’t change. Who knows what parts will be needed, but rest assured your regulator or bcd will be returned to you better than how you remember it working. Debbie is also the mom of the group. When we travel, she takes care of all the land-based planning. If there is a group doing something, Debbie makes sure everyone is well taken care of. If something isn’t right, let her know. She will go to battle for you to make sure it is. It’s a family operation and she is the Mama Bear.


John R Sims ~ Instructor #51924

Instructor & Assistant Store Manager

Contact:  johnsimsjr@scubastuff.com

Little John is the baby of the family. Quite nearly born in the dive shop, he has well over “20” years experience in the store, including 6 years of teaching. At 6’3″ he isn’t so little, but he is the virtual personality of the store. Bringing both the talents of his Mom and Dad to bear, when you work with Little John, you get the whole package. With an Instructor Trainer rating he can teach you how to be a scuba instructor while rebuilding your regulator and not even work up a sweat. If your nervous, he will calm you. If you need a little motivation he will cause you to reach for the stars, all the while making sure you are safe and comfortable in our ocean environment. He is also our “go to guy” for underwater hunting. You can’t help but smile when you’re spending time with Little John. As the president of our Dive Club, he helps provide you with all the activities you could possibly want to try in diving. He is a great mentor, teacher and all-around Big Brother (did we mention 6’3″).

Mike Sieverman

Instructor & Public Safety Diving Expert

Contact:  mikes@scubastuff.com

A retired Police Officer and U.S. Army Veteran, Mike brings an Esprit d’ Corps to the Ocean Gear family. While not blood related, Mike typifies family in the shop. He will joke with anyone, help everyone who walks through the door and be the first person to stick up for you if you stumble. He is family.

Mike is also one of the creators of the NAUI Public Safety Diver course and has his own comprehensive training program for Public Safety Diving. His is the only program in Southern California that is POST approved and recognized by Police, Fire and Sheriff Departments for proper dive training.

Mike is a true team player. He is willing to try almost anything if it means the diver will benefit in the end. He has willingly been both the innovator and the guinea pig for several of our slightly crazy ideas. He is always ready with a good laugh and brings just the right amount of sarcasm to the project to keep you motivated. He is detailed and meticulous as his military background demands, but is flexible and reasonable to figure out the perfect solution to some unique circumstances. You will really enjoy learning and diving with Mike.

Marilu Bustamante

Instructor & Co-Director of Social Media

Contact:  marilu@scubastuff.com

Caitlyn Tassin

Instructor & Co-Director of Social Media


Matt Muldorf

Staff Instructor, Father of 3 small children &  Bon Vivant

Rachel Cushman

Staff Instructor & Assistant Dive Safety Officer: Aquarium of the Pacific


Masa Komura

Staff Instructor, Equipment Technician and, quite simply, the nicest guy on the planet!