<human>: Can you give me a shortened version of the text?

My story is that my friend was at the beach with her family one time. There were these massive sand dunes and her and her brother were standing at the top of one.

Their dad yelled out for them to run down the sand dune, so her brother did. She decided she could do it too so she started running down.

One of her feet just "turned into mud" and she fell onto her face and began sliding down the dune on her face. She flew for a little bit before she hit the sand. She slid all the way to the bottom of the sand dune on her face and her dad laughed so hard. And I do too every single time she tells me or it we bring it up.
<bot>: Friend started running down a sand dune and tripped, falling onto her face and sliding the rest of the way down