Commensalism is a form of nutritional relationship between tow living organisms in which one of the organisms (the commensal) benefits and the other is unaffected in any way.
<em>In this case, the shrimp benefit from the sea cucumber by getting its shelter and get moved around while the sea cucumber is not in any way affected.</em>
Protists are a diverse collection of organisms that do not fit into animal, plant, bacteria or fungi groups. While exceptions exist, they are primarily microscopic and made up of a single cell (unicellular), according to the educational website CK-12.