Question

Do aquatic plants have stomata?

Answer 1

Stomata are the small pore-like structures present in the leaves, and stems. Aquatic plants have four types. Types of aquatic plants are floating plants, submerged plants, algae and emerged plants. Most of the submerged plants don't have stomata. They are completely immersed in the water. They get nutrients, water and dissolved gases from the water so they don’t have stomata on the surface.

Complete answer:
All aquatic plants have stomata on the upper surface of leaves or it will open all the time. Stomata are used in the transpiration process. Transpiration is the process of removing water from the plants as a water vapor to the atmosphere. In the submerged type of aquatic plants all parts are placed in the water. So they don't do transpiration. But in floated plants they have stomata to perform transpiration.
In aquatic plants stomata are present in the upper epidermis because they are in floating condition. So they don't have stomata in lower epidermis. And also at lower epidermis there is the direct trade of gases between leaf and atmosphere.
Stomata is also absent in the mosses. It is also covered by the water. The plants which are surrounded by the air must need the stomata. Stomata are used to get the carbon dioxide from the atmosphere because it absorbs the excess water inside the plants.

Note:
Aquatic plants have stomata except hydrophytes. They are getting their essential nutrients from the water body. Stomata perform photosynthesis and give the food to plants and also maintain the water content in the plants. Vascular plants have a large amount of stomata. Angiosperms are capable of growing completely inside the sea water. So this is the example for hydrophytes.