I found a horseshoe crab (Tachypleus gigas) half-buried in the sand. RY pointed out theres a larger one below. The smaller horseshoe is a male clinging on the back of the larger female, whereby she will lay a batch of eggs in the sand and which will be fertilised by the male later.
This is my first time seeing an acorn worm (Class: Enteropneusta, Phylum: Hemichordata) working its way in the sand. The yellow tube is the end of the worm where it excretes processed sand.
There were also many moon snails moving actively searching for their next meal.
Of cos, there were the stars, above is a sand star (Astropecten sp),
And a juvenile knobbly star!
This scaly thing on the gong gong is a chiton (Class: polyplacophora). They are related to snails, having a muscular foot and using a radula to scrape algae, bryozoans and bacteria.
The thorny sea cucumber (Colochirus quadrangularis) exposing its feeding tentacles in the water. There were also many of them clustering on fan shells, probably to get a good height for suspension feeding.