Singapore

Singapore is not known for diving, largely due to poor water visibility (caused by silt, from past land reclamations).  However, if you like muck diving (limited visibility) Singapore has a lot to offer.  In the waters around Singapore, you can find Nudibranchs in large numbers, turtles, sea snakes, barracuda, frogfish, sea horses, and many more.  If your lucky the local dolphins may visit you during your surface interval.

Malaysia

Malaysia offers some of the world's Top 10 diving destinations, like Sipadan.  Diving on the Malaysian peninsular is usually at the island located on the East coast.  While diving in East Malaysia has a wide area with good dive sites.

Indonesia

The Indonesian islands are spread far across Southeast Asia and offer a variety of diving destinations.  Less than an hour boat ride away is Bintan/Batam, while visibility can sometimes be on the low side it is a convenient getaway from Singapore.  Bali is obviously another popular dive spot, with diving around Nusa Penida or Telumban.

Brunei

Brunei actually has a lot to offer for divers, conditions can vary depending on the time of the year.  Brunei has many wrecks, some from wartime others from peace times.  The diving is generally land-based by speedboat out to the dive sites.