Echinoderms usually refer to creatures with little bone structure that live under the sea.
The star fish has a very convoluted excretory system. It is convoluted in how simplistic it is. It is so simplistic that it is complicated to understand how simplistic one organism could excrete so simplistically. The start fish has no excretory organs. They have a water-vascular system that is made up of cells devoted to taking in waste and passing it along through tiny openings. They pass it along to an area known for star fish as the tube feet that put out excretion in the form of nitrogenous waste (urine).
The sea cucumber, like the star fish, has the organ known as tube feet. But in the sea cucumber the tube feet are used to absorb nutrients instead of excreting waste. After being taken in by the tube feet, the nutrients are broken down and the waste is sent through an organ called the pharynx. The pharynx links directly to the intestine which wraps around coils several times. Then waste is finally excreted through the anus.
The majestic sea urchin has two primary ways of excreting waste. One involves nutrients being broken down and sent through the pharynx, intestines, and then out through the anus. Much like the cucumber, the instestines wrap around several times. But the other way sea urchins excrete waste is by releasing it in a liquidized form through pores all over the body.