I thought Water Moccasins were much more aggressive than Copperheads.
Generally, yes, but both are in the genus,
Agkistrodon. Young moccasins closely resemble copperheads. Someone may have been chased by a young moccasin and thought it was a copperhead.
That said, I wouldn't be at all surprised to meet an aggressive copperhead. And some rattlesnakes can be quite aggressive.
Some other snakes are notoriously aggressive. These include black mambas and king cobras, especially in mating season.
I remember a video of the late Steve Irwin in Kenya. He foolishly molested a large Egyptian cobra,
Naja haje. It went right after him. So did Red Spitting Cobras,
Naja pallida, if you want to look them up. Pretty snake. It always amazed me that Australian snakes were so docile around him. Very odd.
He got hold of a black mamba (
Dendraspis polylepis) that he finally bagged after a very dangerous effort that nearly got him bitten. He was clearing it out of an African's hut. He made his famous, "I was sweating bullets" quip after that event! Why he thought it might be less hazardous than it was baffles me.
A South African guy named Austin Something (Stevens?) had a similar TV show. He did get tagged by a cobra. I think it was
N.
haje, although Cape/Yellow cobras (don't recall the scientific name) live there, too.
Both men were pursuing the snakes, hoping for "good TV."

Good undertaker opportunity, too...
Oh: someone on another board recently sneered at me that I don't know an asp (viper) from a cobra. Turned out he objected to my writing that Cleopatra died from self-inflicted cobra bite. Legend holds that she committed suicide with an "asp." I think someone made a bad translation of Greek, Latin, or Egyptian sources. It was surely a snake, but Egyptians of high birth who were condemned were often slain by cobra bite, relatively quick and painless. A viper of that region, probably of the genus
Echis, causes an agonizing, slow death. Reptile experts seem to agree that the cobra was a far more likely choice for a queen wanting to die. Cleo may well have had access to a puff adder (
Bitis arietans), but that was again a poor choice for a royal suicide, although usually deadly.