Skimboard rental any good?

I recently went to the beach and rented a skimboard for cheap (about 25 bucks for 24 hours) but me and all my friends couldn't ride the thing for more than a few feet before it would sink into the water tossing us off. My question is, would a more expensive skimboard make it easier for us to learn. I notice in YouTube videos the guy's skimboard comes bobbing up on top of the water immediately after he gets off of it. My rental would sort of lazily float back up to the surface sort of half submerged in the water. I believe the brand was zap and it was about a half inch thick and when stood on its end it came above my belly button but below my nips. The beach was Myrtle Beach on the east coast USA. The sand had lots of small and big shells mixed in. We tried high tide and low tide. At low tide the beach was flat  but at high tide the beach had a pretty steep angle but it seemed to work the same no matter what. We would jog with the board and lay it into the ground and try to step into it as gently as we could.