NDU (Naval Diving Unit), which is located at Sembawang camp, is the home of the elite naval divers. The VA (vocational assessment) will assess ur suitablility for the diving course.
Basically, u will undergo a standard 10 week BMT (slightly different from Tekong's BMT in some aspects) followed by a 6 weeks Physical Phase where u will learn the basics of diving. Next is something called Team Building Week aka Hell Week.
This is where u'll be put through immense physical strain and ur physical limits will be pushed to the max. Once u've passed through Hell Week, then it'll be the 13 week diving phase where all u'll do is dive, dive and dive. After which, u would have graduated with a diver's badge (Rank: CPL).
Of course u'll be sent to many other courses after u pass out as a diver, mainly land combat training etc... As a diver, u'll also get the chance to travel abroad, Taiwan mostly.
As for the VA, u'll go through a short swim test (assess water confidence), two NAFPA stations (pull ups and SBJ), medical test (blood test, lung capacity test etc.) and an interview with one of dive school's instructors (usually Warrant Officers).
Good luck my friend! Haha.....