awww, look at the baby crab!

crab larvae saying hello
Originally uploaded by nature adrift

There's an entire world of seemingly alien life adrift in the ocean currents. There are plant forms, or phytoplankton, and animal forms called zooplankton.

Not all plankton are microscopic. Some can be easily seen without any special instruments and this crab larva's about 3 mm, comparable with a half-grain of rice.

Basically, the defining characteristic of plankton is that they just drift with the ocean currents; they cannot swim strongly enough to "go against the flow." So, technically, jellyfish can be considered plankton and some of them are quite large.

Many sea animals start life as plankton and then, once they're bigger, they'll settle down all the way to the sea floor or be strong enough to swim wherever they want. I just love this guy; he looks like a Pokemon doesn't he?