Take a minute or two to think about where is the best place to toss the rope from. Ideally, you want good footing and a place to brace yourself. Now lets think about the swimmer. When they grab the line, they will swing in a large predictable circular arc towards shore. If they grab the line 20' from your side, they will land 20' below you. Look at the landing zone, is there a ledge, hole, or strainer? If the answer is yes, consider an alternate place to throw from. You can adjust the landing zone a bit with a dynamic belay. Ask someone to station themselves at the landing zone to assist the swimmer getting out of the water.