The Northern California Fly Fishing Board

Shawn covered most of the trespassing law. The property must be posted every 1/3 of a mile then crossing results in trespassing. Even if the property isn't posted with signs an you are engaged in certain activities, if I remember correctly hunting was one, then you are trespassing. If the land owner asks you to leave private property and you do not it is trespassing. If you cut a fence or do other damamge that is vandalism a seperate offense. Also the property owner has the right to make a citizens arrest and law enforcement has to accept the arrest. If you are not sure if it is public land either ask permission or find someone that knows.

Waters are considered navigable if historically the water was used to travel, if I remember correctly Deer Creek is considered navigable waters because Peter Lassen put on an early map that he had taken a canoe up the creek for a distance.