PLEASE NOTE - I have made some changes to the lid since taking the photos. I wanted to reduce the need for supports, so I have added a chamfer to the lid, by the handle. There is now a circle, with a diameter of 29mm, that you can bridge, if your printer is well-tuned, or add some supports to. Nothing else in the model needs supports.

The Sandy Safe is meant to be buried in the sand, keeping the top of the vault and the lid on the surface so you can open/close it. Once buried, you can hide the Sandy Safe under your towel, and store your valuables in it. It is roughly 10" tall and can easily hold 2-3 phones plus a wallet, keys, and more. You can print an optional TPU gasket to attach to the main body for added water/sand protection. You can also print an optional flag that mounts to the handle, if you don't want to hide it under your towel. 

The threads on the outside of The Sandy Safe do not allow you to twist the vault into the sand.  You'll have to dig a hole and burry it. However, I am hoping those threads help hold it in place, so it's no so easily pulled out.

Choose your own print settings, but 0.2 layer height worked great for me. I printed mine in PETG since it will be outdoors in the heat.  For added strength you could bump the perimeters walls to 3-4.