A Marine with 2nd Reconnaissance Battalion, 2nd Marine Division allows himself to sink to the bottom if the pool while conducting 5 bobs with a mask in his mouth at the Courthouse Bay Training Tank aboard Camp Lejeune, N.C., March 20. Approximately 20 Marines from 2nd Recon Bn. are participated in a two week pre-dive course in which they conducted exercises that would ready them for Combatant Diver Course.