Camp Pendleton Marines low crawl through a mud pit as they participate in the challenge of the 2012 Hard Corps Race Series World Famous Mud Run near lake O’Neil, June 1. The Mud Run is a challenging 10K run with hills, tire obstacles, river crossings, two 5-foot walls with mud on both sides, tunnel crawl, slippery hill climb, and the final 30-foot mud pit.::r::::n::::r::::n:: - Camp Pendleton Marines low crawl through a mud pit as they participate in the challenge of the 2012 Hard Corps Race Series World Famous Mud Run near lake O’Neil, June 1. The Mud Run is a challenging 10K run with hills, tire obstacles, river crossings, two 5-foot walls with mud on both sides, tunnel crawl, slippery hill climb, and the final 30-foot mud pit.::r::::n::::r::::n::