Hyde Park has the Serpentine, a little lake, which is a good place for swimming or boating. The Serpentine is a popular spot for various recreational activities, including paddle boating, rowing, and even enjoying a leisurely walk along its banks. Additionally, the Serpentine Lido offers a designated area for open-water swimming during the summer months. Whether you're looking to cool off with a swim, enjoy a boat ride, or simply relax by the water, the Serpentine provides a picturesque setting in the heart of London.