Hello Emma,
Seaweeds photosynthesize in the same way as terrestrial plants.
The green seaweeds use the same parts of the light spectrum as land
plants, namely red and blue-violet. As the light moves through water
same of the wavelengths (colours) are absorbed by the water. The
brown seaweeds have a special pigment called fucoxanthin which helps
them use the green parts of the spectrum as their energy source.
Red seaweeds contain a pigment which can use the blue part of the
spectrum. Because the green and blue parts of the spectrum can go
deeper into the water than the other colours, the seaweeds which
use these colours in photosynthesis can live deeper in the water.
This is way the green seaweeds are found in shallow water, the brown
seaweeds in deeper water and the red seaweeds below the brown seaweeds.
If you need any more help, please let me know. There is some information
on feeding in green plants on the Open Door Web Site at http://www.knockonthedoor.com/
Good Luck
Shirley Burchill
Just how big is the Elephant ?
HomeWork Elephant is receiving over
100,000
page
impressions per month (and growing).
Check-out
the 
