In water hyacinth and water lily, pollination takes place by:

Pollination by water is quite rare in flowering plants and is limited to about 30 genera, mostly monocots, e.g. fresh water plants like Vallisneria, Hydrilla, marine water plant like Zostera (sea grass). In a majority of aquatic plants, the flowers emerge above the level of water and are pollinated by insects or wind e.g. Water hyacinth and water lily are pollinated by insects.