Expeditions
SV Infinity was anchored just north of Pulau Baru. From here, we conducted two snorkeling expeditions to the uninhabited island of Semut, through Selat Onas (the channel running between Semut and Matak with coral reef formations) and to Tokongbelayar (small rock island with fringing reef about 2 nautical miles offshore from Semut).

Island observations
The island of Semut belongs to Conoco Phillips who have a base for their offshore oil operations on the neighboring island of Matak. We landed on the beach on the S/SW side where there is a small mooring to tie off. The beach is soft white sand with some coral rubble. There were clumps of oil washed up on the beach (also observed at Penjalin) plus a lot of trash on the beach and on the seabed in the shallows. There is a coconut grove and some mangrove areas edge the shore. We heard a bird which had an owl-like call and saw a white-bellied sea eagle. On several of the beaches in Semut we found flour sacks filled with sand. We observed in Terempah a week later sand bags being unloaded at the main dock. It is used primarily in cement construction.
A path leads across the island to a beach on the NE side which is also soft sand with corals growing all the way up to the shoreline. It takes about 7 minutes to walk across the island. There is a large rock which has ‘Conoco Phillips’ carved into it. There is a recently poured cement area, either a helicopter pad or a foundation, about halfway along the path crossing the island.

Reef observations
On the reef fringing the south SW side of Semut we snorkeled in the shallows where we found patches of hard coral on a sand substrate. There is a high presence of filamentous algae. There are some branching Acropora spp. colonies plus some rubble and dead coral. There are fields of Porites spp. fingers which looked like they had been broken apart in the past; large boulder colonies split to create canyons between them about 2 meters deep. (Photo to right: Selat Matak Channel)

Selat Onas is a narrow channel running between Semut and Matak (see photo below). It becomes increasingly shallow towards the east until it is about 20 cm deep with a sand bottom, impassable by zodiac at low tide. There are reef patches fringing the south side of Semut and one very interesting ridge of reef which spans the width of the channel. This ridge has large areas of foliaceous Montipora spp. and branching and table Acropora spp. colonies. Both genera were damaged by crown of thorns seastars. There was also evidence of dynamite fishing but it did not appear to be recent damage; areas of broken corals and a significant presence of macroalgae

At Tokongbelayar, there were about 15 fishing boats less than a mile off the island, trawling with a hand line. While snorkeling we sighted four blacktip reef sharks. One of them was particularly lively, swimming very fast and decisively beneath us. The reef around the rock comprises a dense population of small coral colonies with small table Acropora spp. colonies dominating and generally in a healthy condition. There is some macroalgae between the colonies. We observed one small Acropora spp. colony which was completely white, possibly bleached or recently predated by crown of thorns. There is a long shelf extending northwards from the island before it drops off.

Turtle observations
We sighted two turtles while snorkeling in the Selat Onas, both too far away to be identified.

crown of thorns damage on Montipora spp. and Fungia spp. colonies on the ridge in Selat Onas

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