You look at your IDC assignment sheet and you read, assignment for open water…Controlled emergency swimming ascent…your feel a small knot in your stomach and gulp. The CESA, as it is more commonly known is one of the more technical dive skills that you will be training to teach during your PADI IDC. It is covered in both confined water and then again in open water. During confined water, you will practice the ascent, simulating the swim horizontally. The idea behind the exercise, is in the unlikely event that you run out of air and your buddy is not nearby, you can safely get to the surface. 
With all of your scuba equipment in place, you would take your last breath, hold up your low pressure inflator and arm, then kick towards the surface, no faster than 60ft a minute, continually exhaling, making an aaaaaahhh sound. Remember, no breathing in as you “have no air” in your tank, and you can’t hold your breath.
Demonstrations in the confined water can be done, swimming towards your students, because as always, you want to make sure that your students can clearly see everything. You can also simulate weight drop and oral inflation in the confined water, once a straight line swim has been successfully achieved. This adds a even more realistic element to the skill and prepares them for the open water.
Once in the open water,one of the important parts is your briefing. Checking out the PADI instructor manual, in the open water course section, outlines the procedure for briefing. There are very strict guidelines following all the points you have to cover, including mentioning;
- Don’t drop your weights
- Kepp your regulator in your mouth
- Swim no faster than 60ft/18m a minute
- orally inflate at the surface
With the new open water course update, these points are now included on the new open water slates. no more writing out of all of your points for the briefing, it is already done for you.
When completing, watch your depth. The standard indicates that you must execute the skill from a depth of 6 – 9m. During the confined water it is a distance of at least 30ft. Make sure you know your distances and depths. Easiest thing, get a reel and mark your distances.
As an instructor, it is very important that you keep control of this exercise. For this reason, you always perform it with a down line. You, as the instructor must maintain contact with the line at all times, and with your student. This can be done in a variety of ways including with your hand, around your leg or through the crook of your arm. You can maintain contact with the student during the CESA by taking the shoulder strap or holding the cumber-band. A popular approach is to then have your additional hand over the regulator of the student, so allowing you to feel as the student is exhaling out as the regulator will vibrate. From this position you can signal the student clearly, stop them, and make sure they are performing the skill correctly. During a PADI IDC it is a great thing to practice the skill, and more than anything, practicing the execution with a student.
So, when you see it written on your assignment sheet, don’t panic, take a deep breath, and go perform an outstanding Controlled Emergency Swimming Ascent!