U.S. Marine Corps Lt. Col. Thomas Waller, commanding officer of 3d Force Reconnaissance Company, 4th Marine Division, Marine Forces Reserve, calibrates a depth gauge prior to conducting dive training in Mobile, Alabama, Sept. 25, 2021. Dive training enables the Marines with 3d Force Reconnaissance Co. to maintain and improve their diving skills as well as building confidence in themselves and their gear. (U.S. Marine Corps photo by Cpl. Brendan Mullin)