The Deep-Cheep (also spelt as Deep Cheep) is a enemy in the Yoshi series appearing in New Super Mario Bros. Wii and Yoshi's New Island. They are a variety of Cheep Cheep that is green instead of red. They originally debuted in New Super Mario Bros. as enemies found in 6-5.
New Super Mario Bros. Wii
The Deep-Cheep appears as a semi-common enemy in New Super Mario Bros. Wii. In this game, they act like a basic Cheep-Cheep but will swim toward you if you get too close. Unlike the more aggressive Spiny Cheep Cheep, Deep-Cheeps will leave you alone if you move out of range. They only pursue you if you move in their direction. Deep-Cheeps can be defeated with fireballs or a Starman and can be frozen with ice balls. Larger variations of the Deep-Cheep also appear called Mega Deep-Cheeps.
Yoshi's New Island
Deep-Cheeps later appear in Yoshi's New Island they are only found in Submarine Yoshi sections where they main serve as obstacles they swim in a wide wave pattern similar to the Rip Van Fish and Piscatory Pete.