I heard they Marine Corps did away with the jump portion in the CSWQ but could not find anything to substantiate it. I am sure those guys at TBS can confirm or deny this. That may very well be a reason.
It dates back to WWII and ships being abandoned from sustaining combat damage. You may well have had to leap over the side and had to get over the fear factor before you had to do it for real as well as learn how to cross your arms to avoid injury. People who are afraid or hesitate to jump from that height can really slow the evolution down. It's critical to get in the water and away from ship ASAP as you can get sucked down with it or get fragged by explosions. Tell me they haven't dropped the underwater swim with simulated burning fuel on water?!?