After serving in WWII Nick was accepted for training as a Swimmer Scout in the 1st Beach Reconnaissance Platoon of the Marine Corps. In 1950 he began his recreational diving career and was part of the first formal underwater instructors course conducted at Scripps Institute of Oceanography in 1953. The following year Nick began working with the Los Angeles County Instructor training program and served on its board of directors for twelve years. He continued with his education in diving and was certified as an instructor by NAUI, SSI, YMCA and NASDS, providing him with a very wide perspective on the quality and contents of all the training programs in the United States.
In 1970 Nick became PADI's first and only executive director. At the time PADI had only 234 instructors, a number that increased to 12,000 worldwide under his watch. The next year he conducted a survey on diving classes throughout the U.S. and wrote the first "Standards and Procedures Manual" for instructors, followed very shortly by his manual "The Basic Scuba Course" which was a step-by-step comprehensive training manual for basic diving certification. Nick's third manual, "Open Water Training" probably changed the diver training more than any other publication. It was the first effort to incorporate multiple open water dives in the training process which was key to making the sport safer.
Nick formulated a dive training program for PADI consisting of five open water dives and then implemented it under the new certification of "Open Water Diver." He went on to write a series of specialty courses for those who wanted more advanced or specialized training, but who were not necessarily interested to proceed on the path to instructor. The industry benefited enormously from the influx of more experienced, confident divers who were safe in open water conditions, continued diving and training throughout their lives.
Over the years Nick has assembled a museum of historical diving equipment that is unequaled. The Historical Diving Society recognised Nick's immeasurable contributions by creating The HDS Nick Icorn Diving Heritage Award, which is presented annually.