Which type of aquatic plant is primarily found at shallower depths?

Emergent plants are primarily found at shallower depths in aquatic environments because they have adaptations that allow them to thrive in these areas. These plants typically grow in wet soil with their roots submerged in water while their stems and leaves extend above the surface. This characteristic enables them to access sunlight for photosynthesis while also providing habitats for various aquatic animals and insects.

In contrast, submerged plants are entirely underwater and usually inhabit deeper waters where they have the necessary adaptations to survive without direct access to sunlight or air. Floating plants, while they are found on the surface, do not anchor in the soil and require open water to thrive. Terrestrial plants, however, are not aquatic and do not thrive in water environments at all. Thus, emergent plants are uniquely suited to shallow depths due to their structure and life cycle, making them the correct answer.