According Christies:

We are grateful to Till-Holger Borchert, chief curator of the Groeningemuseum, Bruges, for ascribing this previously unpublished panel to the Workshop of Patinir, on the basis of photographs, and for dating it to c. 1530-40. While there does not appear to be a direct prototype for this composition, it can be compared with a painting of the same subject by Patinir in the Escorial, Real Monasterio de San Lorenzo, and another attributed to him in a private collection (R.A. Koch, Patinir, Princeton, 1968, p. 81, no. 28; M.J. Friedländer, Early Netherlandish Painting, Leiden, 1973, IXb, no. 247, pl. 239). Furthermore, the castle on the right shore recurs in a Saint Christopher, attributed to an Antwerp Mannerist c. 1520/30(?), in the Musée des Beaux-Arts, La Rochelle.