I have read a note from Dr E of Fife asking how lakes can work as any kind of a boundary in a deer park, since deer can swim. Dear Dr E, it’s all in the way the lake edge is constructed – wharfed or beached.
It is true that animals can drink at a sloping beach and wade in so far that they find themselves swimming, but they will not step down over a vertical edge if they cannot see the lake bed. If by chance they do get into the water, it will still be impossible for them to get out on the other side if the water is deep enough and the edge is wharfed, as it was at Longleat, and as one can still see it at Sherborne, Burton Constable and Langley – and that’s taking only three places at random.
Though himself unfathomable, the 18th century gardener, Capability Brown, like his unctuous successor, Humphry Repton, recommended depths of three to four feet and no more for a lake, so larger animals could have waded through, but only if they could get across the vertical edge.