Kohl's currently has a lot of swimsuits in their clearance bin with items on sale for $4 and up Plus shipping is currently $0.99 per item. You can also save an additional 10% with code NEW137.
They seem to have sold out most of the cheapest mens swim trunks. But there are still a lot of womens swimwear items for $4 range.
Plus you can get an extra 4% cashback if you buy via Ebates.
I heard about the Kohls sales at Slickdeals.net