Way to go Denis
The replies about the "Guard's" (Self appointed or not) bad behaviour , , , , I agree with you.
Also, claiming "authority" if he actually doesn't, then the bloke could have approached it from that stand point, with diplomacy. And yes, report that behaviour to the relevant Authorities, which includes the "Marina" people.
And again, I totally agree with you about challenging the "legalities".
Here in SA, we have Westlakes. A large man-made waterway, lake , , , , large investment for primarily residential frontage with parks, beaches and other public access areas. There are numerous fishing restrictions and fishing restricted areas , , , , be them Government, Council or Strata/Community facilitated. Works well most of the time, as it accommodates the resident's rights to peace as well.
We wouldn't like different groups of cars in front of our place of residence with the car occupants "hanging about" most days or nights , even if they were legally allowed to, , , , so it is nice to give that same courtesy to the lake's residents.
Like I said, works well most of the time.
Plus, with Westlakes, I can fish equally bad in any location, so no need to show the residents my ineptitude at fishing
Regards, Bugs