Diving in Singapore waters can be challenging due to the lower visibility. This is caused by heavy traffic of naval craft of all sizes. About 2 years ago, my wife and I dived around Pulau Hantu. Visibility was poor and there were strong currents. We did not particularly enjoy that dive; but we had a great time with our fellow divers. We haven't returned to dive around Pulau Hantu recently. Singapore is taking additional steps to establish a marine sanctuary for the benefit of all divers around the Sisters' Islands. I hope you get a chance to return to Singapore to dive in the future.

PS: I checked out your comprehensive post on coral spawning. Enjoyed reading it. The accompanying photos were also great! Upvoted it.