Wikipedia
Yontaifib (Batalyon Intai Amfibi - Amphibious Reconnaissance Battalion) is an elite recon unit in the Indonesian Marine Corps, just like Combat Reconnaissance Platoon ( Indonesian:Peleton Intai Tempur - Tontaipur) in the Army ( Strategic Reserve Command). This unit is used to be named Kipam (Komando Intai Para Amfibi - Para Amphibious Reconnaissance Commando).
To obtain a certification of amphibious reconnaissance, a regular Marine has to first pass a tough selection and then pass the nine-month rigorous training program that contains the most difficult curriculum. Thus, this amphibious recon certificate is very similar to commando certificate in Kopassus.
To become a Yontaifib troop, a candidate is selected from the Marine Corps who has already fulfilled the thorough mental and physical requirements, and who at least has actively served the corps for two years. The certification of amphibious reconnaissance is so difficult that the passing rate of these candidates in each class is only ten percent.
One of the most challenging exercises in this certification program is to swim for three kilometres while the hands tied behind their backs and their feet bound together. Due to the hands and feet being tied the swimmer must learn to relax and move his legs and feet in a fluid motion similar to that of a dolphin. This type of training is designed to increase the candidates confidence in the water and also allow him to survive if he is caught by the enemy and must escape.
The escape experience by an American POW who was hog-tied and then tossed into the Mekong River to drown. He was able to survive despite being bound and proved that a man can swim with his hands and legs tied if he puts his mind to it. The technique was adopted by the US Navy SEALs and still used to this day. Other Naval Special Warfare units soon followed and now is a standard part of selection and training.