<p>Fig. 4. From left to right: the three main types of plants in the ocean include sea grass (a true vascular plant), macroalgae (known as seaweed or limu), and microscopic phytoplankton (often single-celled).</p>

Fig. 4. From left to right: the three main types of plants in the ocean include sea grass (a true vascular plant), macroalgae (known as seaweed or limu), and microscopic phytoplankton (often single-celled).

Images courtesy of the NOAA Photo Library