Hi, Water typically will not reach higher than 6" and all Blast Zone Inflatables are currently equipped with water outlets to keep the water from rising any higher. However, as you mentioned, it ultimately depends on how level your ground is, as water can pool up in areas where the ground is lower below the splash area. We advise completely level ground. Additionally, all Blast Zone products are rated for children over 3, as all products in this toy category should be. This is to comply with various safety laws and practices. Sincerely, Blast Zone Support