Marines from 2nd Reconnaissance Battalion, 2nd Marine Division practice tying knots on the pool deck before entering the water to retie them while underneath the water at the Courthouse Bay Training Tank aboard Camp Lejeune, N.C., March 19. Approximately 20 Marines from 2nd Recon Bn. participated in a two week pre-dive course in which they conducted exercises that would ready them for Combatant Diver Course