Get up to 40% off swimming pools at Walmart.com as a 4th of July special. Some best bets are this Summer Waves 18' x 42" Metal Frame Pool which drops from $349 to $209 or this Intex Mermaid Play Center Pool for $39.97 (the only site we found it under $40, and well-reviewed at Amazon. Shipping is free at $50, but some of the larger pools have a surcharge (all of them can be ordered for free store pickup). Sales tax is charged in most states.