Here is a big momma dark fishing spider, in De Soto National Forest, Mississippi. With legs, top to bottom here, she is about 6 inches. They don't weave webs, but instead wait and ambush. Usually near the water's surface, once they detect ripples they will run across the surface of the water and subdue their prey using their foremost legs, which have small claws. They'll take anything they can, including little minnows.