In addition to knocking 50% off all of its bestselling swimwear and sandals , Madewell is also offering an extra 30% off its stacked sale section . Both discounts can be applied at checkout by using one very on-the-nose promo code:If you're in the market for a new pair of effortlessly cool slides or a figure-flattering one-piece suit to laze around your AC unit in, then don't dillydally on carting up these marked-down essentials while they're still in stock — sizes are already starting to sell out.