A Navy SEAL assigned to Pearl Harbor's Delivery Vehicle Team One submersible unit died Thursday while conducting training in waters off Bremerton, Wash., the Navy said.

Chief Special Warfare Operator Eric F. Shellenberger, 36 — who completed more than seven combat deployments to Iraq and Afghanistan — died following a diving-related incident, officials said.

Shellenberger was from Bucks, Pa. An investigation of the incident is being conducted, the Navy said.

According to Naval Special Warfare Command, Shellenberger and other SDVT-1 members were in Washington state conducting training using SEAL Delivery Vehicles, a lithium-ion battery-powered submersible used to transport commandos.

During an SDV training dive in the very early morning hours Thursday, Shellenberger encountered difficulties in the water and signaled for an emergency ascent, the Navy said. Upon reaching the surface, he was non-responsive and rescue breathing was administered.

Shellenberger was taken to a pier, where regional emergency medical technicians continued rescue efforts. He was transported to Naval Undersea Warfare Center Division Keyport, where advanced life-saving efforts (including advanced cardiac life support and treatment in the recompression chamber) continued without success.

"This is a heart-wrenching loss for us and, most assuredly, the Shellenberger family," said Adm. Edward Winters III, commander of Naval Special Warfare Command.

"The strength of our small, close-knit community is in our exceptional personnel. Eric was one such individual. He bravely and willingly accepted the risks inherent in training for and carrying out special operations missions."

Shellenberger reported to SEAL Delivery Team One in Hawai'i in September 2005. He was SDVT-1 and Naval Special Warfare Group Three's Sailor of the Year in 2007.

Shellenberger completed more than seven combat deployments to Iraq and Afghanistan, including deployments as an assault team leader in Ramadi during the Sunni Awakening in 2006-2007, as well as a combat deployment as a Force Reconnaissance Marine to Somalia before transferring to the Navy, officials said.

Shellenberger is survived by his mother, stepfather, father, two brothers, grandmother, fiance and extended family.

"Eric will be dearly missed. We always considered him to be a true hero, and he will be in our hearts forever. We love him and will cherish his memory. He will never be forgotten," the family said in a statement.