Sigma 50-500mm f4-6.3 APO DG HSM. Shown at 50mm, it extends quite a bit to 500. Summer swim season is outdoors, and this is a great all in one lens in outdoor light. In spite of its nickname, after shooting the Nikon 200m f2.0 and 200-400 handheld all day all weekend at meets, its actually remarkably light.