Pulau Semakau (North) with 3 giant clams

Pulau Semakau (North) is close to the petrochemical plants of Pulau Bukom and yet has some great reefs. A full team survey today and find 3 giant clams, a seahorse, special sea anemones and more. 

The corals seem mostly alright although there are signs of stress in some colonies. The seagrasses remain sparse.

Today, the Giant Clam team are not with us, working on another shore. So we try our best to find clams and seahorses for them. Bravo to Dylan for finding a Burrowing giant clam (9cm) as soon as we landed. A little worrying to see it has a bleaching bit on its flesh - like corals, giant clams also rely on symbiotic algae to make food from sunlight, and thus can also bleach. Sam Lau found a large Fluted giant clam (35cm) near the reef edge. And Marcus found the another (23cm) near our departure point. And I found a seahorse! Wow, I was so surprised.

As usual, the rest of the team make all the special finds. We landed during a spectacular sunrise. Marcus found the Leathery sea anemone which we rarely encounter. Zen found a Strapweed filefish, also not often seen. There were also 'Nemos', Magnificent anemones and Fire anemones. Richard saw two special flatworms not often seen, while everyone else saw a lot of Spangled flatworms and many different kinds of nudibranchs. Including some mating, and egg ribbons laid.

So delighted that Dr Clarence Sim has captured a view of several sharks peacefully foraging on the reef edge. Great proof of how we often encounter them on our surveys, especially of the more remote offshores reefs. But they are shy and will flee as soon as they sense we are nearby.

Tammy also captured a view of these sharks. Our sharks are NOT dangerous to humans. It is perfectly safe to be on the shore with them if we respect their space. We have surveyed shores for decades, often in the dark among sharks, without any harm to people or sharks.

Sharks are a sign of a healthy reef. Many sharks means there is enough fish for them to eat. So let's rejoice when we see sharks on our shores! We often see sharks cruising the edge of submerged reefs at low tide, probably waiting for the tide to turn. Just as the moment a 'kopi tiam' door opens, the sharks are eager to rush in and be the first to get the fishes. Adding these great clips to our compilation of peaceful sharks seen on our shores.

The team also shared some awesome underwater reefscapes. And sightings of some special corals.

Although most of the corals and cnidarians seen seem alright. The team did see a few corals that were stressed or bleaching. Or had large patches of dying tissues. Including one bleached anemone. 

Within sight of the ongoing Sudong reclamation, there are stretches of rich reefs on Pulau Semakau North. 

The coral situation seems similar to our last survey in Apr 2025. The reef edge remains rich with many well formed healthy corals. Mostly boulder shaped corals, but also some plate corals. There were also many mushroom corals.

I saw about 5 colonies full on bleaching, some were stressed (pale or pinkish), many corals had dead portions taken over by algae. I saw one Boulder pore coral with bluish grey dying tissue.

Today, I saw many Leathery soft corals on the reef edge of various kinds. I didn't see any that were bleaching, but one had peeling 'skin'.

I also briefly checked the seagrass situation. There remains basically no seagrass in the shallow lagoon which used to have lots of long Tape seagrasses. This is similar to our last survey in Apr 2025. 

In this lagoon, I saw a sprinkle of Spoon seagrass (small leaves) and dense patch of green scum (got scammed, thought it was seagrass) with a little Noble volute in it. I saw one clumps of cropped Tape seagrass. At the reef edge, I did see small clumps of Tape seagrasses with longer leaves (about 30cm). Thankfully, Dr Clarence did a better survey of seagrasses, check out his album here.

The ongoing Sudong reclamation is visible from the reefs on Pulau Semakau North.

Thanks to Zen for taking these great photo of the ongoing Sudong reclamation. It seems to still be in full swing. The pile of sand seems to still be growing taller with huge vessels spitting out sand, excavators moving sand. And other huge vessels working nearby.

From Port Marine Notice No. 55 of 2026 "Reclamation at Pulau Sudong" with effect from 08 Apr 2026 to 07 Oct 2026. The works involve the installation of navigational buoys, removal of metallic debris, demolition of abandoned jetty, dredging works, installation of marine staging platforms for soil instrumentation, infilling works, marine vibrocompaction, stone revetment works, and jetty construction to facilitate the reclamation and jetty construction works at Pulau Sudong.

Here is the location of Pulau Hantu and other nearby shores in relation to the Sudong reclamation.

More about Pulau Semakau

Just as Changi Airport and Changi Beach are not the same even though they are near one another and share a name, Pulau Semakau is NOT the same as the Semakau Landfill. The Landfill was created by destroying all of Pulau Saking, and about half of the original Pulau Semakau by building a very long seawall. Fortunately, the landfill was constructed and is managed in such a way that the original mangroves, seagrass meadows and reefs on Pulau Semakau were allowed to remain. It is NOT true that the construction of the Landfill created the marine life found on Pulau Semakau. The marine life was there long before the Landfill was built.

What is the fate of Pulau Semakau (North)?

Pulau Semakau (North) is likely to be affected by the massive reclamation outlined recently in the Long-Term Plan Review.

The Singapore Blue Plan 2018

Pulau Semakau and nearby islands and submerged reefs have been recommended by the Singapore Blue Plan 2018 for Immediate Conservation Priority. The Blue Plan recommends the intertidal and subtidal marine areas of Pulau Semakau and adjacent Pulau Hantu, and Pulau Jong to be designated Marine Reserve.

The Blue Plan highlights that Pulau Semakau and its associated patch reefs comprise many ecosystems: coral reefs, mangrove areas, intertidal sandflats, seagrass meadows, and coral reefs. The subtidal area of Pulau Jong is larger than the terrestrial area. Pulau Hantu is a popular dive site has seen increasing interest in the past decade due to biodiversity awareness. If protection is accorded to these three islands, zonation plans for use can be implemented to manage tourism and human impacts.

DOWNLOAD the Plan, SUPPORT the Plan! More on the Singapore Blue Plan 2018 site.

Photos by others on this survey

Che Cheng Neo


Richard Kuah


Rui Quan Oh


Zen Xuan He


Marcus Ng


Tammy Lim


Lon Voon Ong


Clarence Sim


Others on this trip: Yan Le Su, Ian Mun, Dylan Seng, Sam Lau, Chui Qing