Seaweed

Seaweed (ワカメ, Wakame) is a type of deep sea creature (although they are plant-like algae) found in.

In New Leaf
Upon the players' donating the seaweed to the Museum, it can be found in the large pool in the first room of the ocean exhibit, along with many other species of deep sea creatures. It is found in the corner near the big rock close to the entrance of the large saltwater exhibit. The exhibit has this to say about the seaweed:

"Seaweed can be over three feet long. When its spores attach to rocks, they take root and grow. Seaweed is naturally brown, but turns to the dark-green color we associate it with when cooked. It tends to spoil easily when picked, so various preservation methods have been developed as a necessity. Such methods of preservation are sprinkling ash and drying it out, or boiling it and adding salt."