Knights Ferry Bridge is the longest covered bridge west of the Mississippi at 330 feet (100 m) in length. It’s listed in the National Register of Historic Places.
The river it spans is the Stanislaus river and is fed by New Melones Dam. Not far down stream is the put-in for class I-II rafting (there are a couple rental companies there through the summer). There is a small rapids up stream of this dive location. The river can rise 20+ feet as the dam releases more water. The minimum depth at the bridge is ~20 feet, so that can become 40+ feet of water.
Generally, the water flow is slow at the bridge, due to the depth and width of the river at this location. Diving can be challenging as the water flow increases (controlled my New Melones Dam). You can see all the varieties of river fish (some seasonal runs), tons of crawdads, few freshwater clams, other wild life such as tadpoles to frogs, mosses, etc. This is in the mother lode, so gold is available to a skilled or lucky prospector [verify the laws before prospecting here].