Do aquatic plants have stomata?
According to the book Stomatal function (Zeiger et al, 1987), many aquatic angiosperm plants have stomata (since they have evolved from terrestial plants), while some have reduced or complete loss of stomata.

However, the book also states that:


  ...aquatic plants living underwater are devoid of stomata. Leaves that float in water, which are common in ponds, have stomata on their upper surfaces but lack them on the surfaces in contact with water.