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(it's in the Daz store) is essentially a combo of both an HDRI sphere and a physical beach plane to stand on. This is helpful for props and such...
Here's an example of the Pines Beach set in action, with characters and an extra prop...
There are some other products that do this as well. Some create a raised platform/feature for characters to stand on, with the HDRI surrounding the raised land feature in all directions...
Flipmode's easy environments do this, and are avaiable through various stores (not all in the same place)
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I'm not seeing a lot of good beach options in his collection though... the seaside ones are pretty cool though!
But yeah, just slapping an HDRI in the environment sphere can get you started quickly, although you'll have 'ground shifting issues' you'll need to pay attention to when you change the camera orientation, unless there's a ground plane/feature added (such as what Pines Beach does above).
With the Daz ground shadow function and ground set to 'on' in render settings, Daz will create a shadow at ground level, as if there was flat ground there. If you are just using an HDRI background/sphere, this will make it look like the character is standing on the ground (unless the angle is weird) instead of hovering in a sphere.
Here's some free outdoor HDRI's to get you started (same as the one posted in the assets release thread). No registration required, just pick the one you like, and the size you want and click to download!
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While not necessary, the guy likes donations though if you are so inclined...
As for the other products mentioned by Rich and others above my post, those are actual sets, so if you need a set as opposed to a basic background they are definitely decent options. I'm sure you've probably seen a few of them in a few of the popular games, such as this one...
Sets can take a bit more time to set up, and do consume more system resources while rendering, but if lit well they are excellent choices as well. It all comes down to how much detail and how many features you need in the pic sequences you are setting up...
Edit: just adding this render of a beach scene HDRI, with characters, using one of the HDRIs from Greg's site (HDRIHaven, link above).