Ask anyone from Florida about fishing eel grass. When we fished the St. Johns river or the Harris Chain, we used to absolutely slay them in the eelgrass when the shad were spawning in it. We would throw a spinnerbait or a buzzbait during the shad bite. Bass also loved to bed in it. Many a tournament has been won with spawning fish out of eel grass on Lake George.
It's not the growing eelgrass, it's the 4 bazillion metric tons of dislodged, floating eelgrass. When 9 out of 10 casts results in a fouled hook, it's a pain in the arse.