Pollination in water plants is carried by the technique called hydrophily. It is the mode of pollination from anther to stigma by means of water. ex. in Zostera angiosperm, the pollen grains float below the surface of water coz they hav same specific gravity as that of water.when they touch the stigmas, they coil around later and germinate.
If you have text book of Pradeep's biology the see the page no. 48 of unit 1.