Hi Katie, While the inflatable will have some extra weight to it when it is being used with water, you definitely need to anchor it at all times for safety reasons. However, this inflatable comes with anchoring stakes included. If you are able to set your inflatable up in grass, you can use the included anchoring stakes instead of the optional sandbags. The sandbags are typically purchased in cases where the anchoring stakes cannot be used, such as indoor use. The sandbags allow for weighted anchoring as an alternative. Sincerely, Blast Zone Support