What's important is to observe as many details as possible and give that information to WCO or even leave it as a message because MANY times it's not a one-off violation and the WCO is familiar with the perp...
Case in point - I once observed some POTENTIAL illegal shellfish harvesting at Scott's Run Lake. I called the Regional LE Office and left a message describing the activity and the actors involved.
I got a call back a day later and the WCO was VERY interested and told me he knew all about these folks, was appreciative of the info I provided and that further surveillance was forthcoming. I also found out I could have reported the activity to the Park Rangers...
I don't know if the activity was illegal, if it was that anyone was caught or fined but I still think WCO's appreciate learning what is going on and who is doing what in their regions, regardless if they can catch violators in the act.
I realize for some it's easier to turn a blind eye but people just ignoring bad or illegal behavior emboldens the slugs and they get away with it over and over again...