Of the courses available, I’m most impressed with Jeppesen’s. It is currently taught by the YMCA, NAUI, SSI, PDIC, NASE, and many PADI instructors, and meets the requirements of all other diving certification agencies. They have a good manual that emphasizes the development of safe diving habits, a thorough understanding of diving principles, and a respect for the underwater environment. They’re also on top of the latest research. Using the findings from recent ultrasound bubble detection tests, they’ve revised their dive tables to show much more conservative no-decompression limits than the U.S. Navy tables in common use.