You might find that running in the sand puts extra stress on your Achilles tendons, because of the way your heels can sink in. Hopefully it won't cause you any trouble, but I'd suggest paying attention to how things are feeling as your body gets used to it.
thank you for this advice. I will pay attention to my Achilles tendons. I'm thinking that in general, I should pay close attention to how things are feeling as I get used to the new terrain.