With orders of $25 or more, Amazon offers the Nerf Super Soaker Tidal Torpedo 2-in-1 Blaster, model no. A9460, for $3.70. Plus, Prime members bag free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, shipping adds around $8.) That's the lowest total price we could find by $11, although it was $2 less two weeks ago (which required in-store pickup). It projects streams of water up to 22 feet.
Note: This item offered as part of Amazon's "Add-on Program" and can only be purchased with an order of $25 or more.