The video is a repair of a fiberglass tub using fiberglass this can be a 100% bond . how ever i'm betting your pond prefab is a plastic . the fiberglass can last a few years but i doubt too much more than that. and a caulking a good polyurethane stands as good a chance of lasting a couple yearsWelcome to the forum. Looks like it might be a fiberglass pond?
Perhaps this?: https://shirleyaquatics.co.uk/product/fibreglass-repair-kit/
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