Seaweed and Water plant

Seaweed noun - Plant growing in the sea, especially marine algae.

Water plant and seaweed are semantically related in algae topic. In some cases you can use "Water plant" instead a noun "Seaweed".

Water plant noun - A plant that grows partly or wholly in water whether rooted in the mud, as a lotus, or floating without anchorage, as the water hyacinth.

Seaweed and water plant are semantically related in algae topic. You can use "Seaweed" instead a noun phrase "Water plant".