Ah, but it does: The text is a bit small in this photo, but the sign says (among other things) No Boating, Swimming, Wading
The sign also says you can't harm the wildlife, but it doesn't say a thing about the wildlife getting a free pass on the rest of the rules. All Bird's Dogs must be on a leash! No exceptions! :-)
FYI: This little lake is smack in the middle of Phoenix. The mountain in the background is Piestewa Peak.
Rick