I've been there twice. The water there is always 27-30c and I think a 3mm jumpsuit or a shorty will be fine.
The visiblity is not very good, mostly 15-30m but may get to 50m sometime. By the time I visited there, the water is all greenish and lot of suspending particles....
The dawn dive there is a "must" as you can see a big big big school of bumphead parratfish that line up just next to you and head for the abyss(gotta have a nice wideangle shot). I "managed" to see school of baracudas but don't expect too much. School of jacks and turtles are everywhere!! Along with plenty of white tip reef shark that either petrolling the reef or simply lazing on the sand and taking a nap. I've also seen hammerhead shark in the baracuda point right below 40m, but also don't expect too much. Overall, the fish there are quite tamed and got used to the present of divers, so you can get close to them easily.
The drop off just in front of the jetty of the grand-old-time-resort of Borneo Diver also worth a visit. There is a cave down there at around 20m where the resort had put up a sign and advice diver not to attempt to enter the cave. Some diver had seen bones of turtle there. This drop off used to be the site for nite dives back when the resort on the island was still serving...
I'll recommend Kapalai Resort. It's jetty dive are good for macro stuffs. The rooms are good but gotta note that there is no air-con there. There is NO mosquito(!!) as the resort is built on a sand bar in the middle of the ocean. They usually arrange 3 boat dives and unlimited(!!) jetty dives a day which can keep you busy and drain all your energy.
Hope u find this helpful.
Ringo