The calmer the conditions and the less wind and or current is present, the better the Nettle Net Boat Pool will hold a circular shape. If the pool temporarily becomes oval, kidney shaped, or crescent shaped, no swimming area is lost, it's just temporarily different. All boats (motor or sail) "sail" to and fro on a single anchor. The stronger the wind, the more sailing, until they traverse several dozen feet. Any pool tied to the stern will be dragged back and forth. There are several solutions such as two anchors, stern anchoring, or a shorter rode that could stop sailing (never set too short a rode than would be safe under the conditions). Another alternative is to use a bridle mooring line from your anchor line to a rear cleat or winch. There is a detailed description of this technique in the pool instructions. Lines tied from side tie straps on the pool to outer points on a boat or a dock can help as well.