Once upon a time a neighbour from one street over let his dog crap on my neighbour's lawn. As this man started to move on, I encouraged him to pick up the mess, as any civilized person would. He said he would have to go get a bag, but that of course, naturally, he definitely would. I was out and about anyway, so I had a chance to observe how this was going to come together. Given that I didn't go away, I watched him dawdle and grimace and fuss with the dog until he convinced himself I was there for a while, finally to see him rifle through another neighbour's garbage can in the adjacent lane, to locate a plastic shopping bag. He walked back, picked up the crap with the bag from someone's garbage bin, and carried on with the dog. Problem solved?
I hoped so, so I drove off on an errand, but I'd forgotten the list of things I was heading out for. I circled the block, pulling up in front of my own house, only to see him at the top of the street now, bending down for some reason. He disappeared around the corner, and when I retrieved the list for my errands, I drove up to where I saw him bend down, and sure enough in that exact spot there was a shopping bag full of soft hot dog shit, tucked into someone else's hedge.
I doubt he knew it, but I recognized him and I knew where he lived on the other street. So I drove it to him. As he closed the door to his own home behind him from this lovely neighbourly excursion, he would have seen a bag of steaming dog shit arc toward his house, thrown olympic hammer-thow style. When it struck, I'm ashamed to admit I was amused beyond perhaps what was reasonable, because the whole steaming bag adhered to the side of his house, just above the door, right where it landed.
It just sat there, clinging to the stucco, evidently moulding itself well enough on impact to the contours of the wall to stay put, as I drove away out of the neighbourhood, in a strange flux between anger and laughter and even pity and a wee bit of remorse. Sometimes plans go too well, you know? I mean it just stuck there, barely out of reach, while he watched it happen while his mouth gaped.
Anyway the point is I have a fair bit of empathy for calling litterbugs to account.
I don't understand all the particulars of this beach. If the location were far enough away, and if the person made a deliberate attempt to put it out of reach, and given that a banana peel is compostable, I would be inclined to err on the side of letting it go. In my neighbourhood we have a wooded area where people walk their dogs. The rule of thumb seems to be that you're an ass if you don't pick up after your dog on the trail, but there is no need to chase off into the brush if your dog scoots in there to do his business. I don't think anyone would care if a banana peel were lobbed into the midst of the trees, so I'm kind of modelling my answer on that. Again, I live far from any beaches and I can't quite picture the set-up. Circumstances may vary that would make a banana peel uncouth.
And absolutely if it were a plastic bottle or in a plastic bag, I would be just as forthright.