The lake, which is some way from the house, beyond the ornamental gardens, was considerably extended by Gilbert during his time at Grim's Dyke. Work on digging out the lake began in 1899, with Gilbert himself assisting in the task. Eventually it covered about one and a half acres, with an island in the middle, a punt house and changing hut, and an artificial waterfall that was ceremonially turned on in December 1899. The lake was drained and refilled each year, to keep the water clear, and was stocked with trout. In 1905 the lake was extended again to a roughly rectangular shape, measuring 170 yards by 50 yards. When Gilbert lived at Grim's Dyke he swam in the lake every day from March to September.