Final answer:
Protists are commonly found in aquatic environments like lakes, oceans, and marshes.
They can also live in the digestive systems of animals and the vascular tissues of plants.
Step-by-step explanation:
A protist or protoctist is any eukaryotic organism that is not an animal, plant, or fungus. Protists do not form a natural group, or clade, but an artificial grouping of several independent clades that evolved from the last eukaryotic common ancestor.
Protists are mostly found in aquatic environments such as damp soil, marshes, puddles, lakes, and the ocean. They can also be found in the digestive tracts of animals and in the vascular tissues of plants.
Some protists live in symbiotic relationships with other organisms, including humans. Others are parasites that infect animals or plants. Additionally, a few protist species live on dead organisms or their wastes, contributing to decay.