Buff Duck housing/predators

[oamyers]

Hello all. I have a pair of Buff ducks who have just nested for the second time this summer and for the second time, their nest has been raided. Bobbie nests on a small island in the middle of my 3 acre pond. I would like to put a structure on the island for her rather than making a coop for her on the mainland. She cannot fly, so many of the typical duck box/nesting options are not the best fit for her. What can I do to keep the predators away from her and still allow her to get to the nest? Thanks! Olivia

Below is a picture of the island where the nest is.