Anyone know of a good plant tutorial that I can adopt into seaweed? Hmm… First I need a tut. on bubbles… Now seaweed… What type of scene could he be making… 
first get some sort of reference pic, or at least a pretty good idea in your head, then just extrude a plane a couple of times and shape it into a single piece of seaweed. Duplicate this many times (for a better way to do this, look for a tut on dupliverts) and you have seaweed.
Apply a material before you duplicate it, else you’ll have difficulty doing so.