Dredges are rarely difficult to identify. For spotting balls/diamonds...binocs are /can be important.
Virtually all the time you see pipe and other vessels, even if only commercial looking skiffs with some kind of gear to work pipe.
So if you have no idea what a dredge is or looks like, then yes you at a serious disadvantage. With some idea, I would hope you are looking for the balls or diamonds, or in what direction the pipe is likely to head, fr the "gate" in the pipe is all else fails or last resort, stop and ask which side.
If one has no idea, one of those little skiffs or tugs is usually running around to warn of the unaware.
Yep, people do hit the pipes, with usually a worse situation for the boat than the pipe.
This all goes back to the arguments about experience. One might boat for years and never come across a dredge....it's what one does when in doubt that really counts.