Sponges

Water is drawn through the small holes in the sides from outside into the interior cavity of the sponge. While the water passes through these small holes oxygen and food is filtered out. The water leaves the interior cavity through the larger openings.

Curaçao has several dive sites with a lot of big sponges, especially around 70 - 100 feet. Lots of big orange elephant ear sponges and barrel sponges. Inside the barrel sponges sometimes a big King Crab hides.

This is a very small type of sponge, called the Variable Boring Sponge. The name describes its behavior. The sponge bores into the coral. From the outside there is no visible damage to the coral, but inside the coral the sponge forms big holes. The holes in the coral are made by secreting an acid.
This picture is made with an extension tube 1:2 (half life size). So the tubes on this picture are less than an inch long. Its color is very bright even under the dim conditions underwater.

This sponge is an encrusting sponge. It grows on the surface of (dead) coral. Its name is Star Encrusting Sponge. The canals form the 'stars' on the surface. These canals are the openings through which the filtered water leaves the sponge.

This picture is also made with a 1:2 extension tube mounted between the camera and the 35 mm lens. The location is 'Small Curaçao' a small deserted island South East of the East point of Curaçao.