Creeks & ponds - question for anyone - put here because I have a ctl/mtl

First -- looking to help a friend with a creek issue. It's not a big creek...they want to carve out an area for the horses to get in, drink etc. They have dug out the creek side a couple of times and it apparently keeps filling with silt or creek debris and is sort of quicksandy after every attempt. I haven't seen this yet but as I understand it is probably clay based creek that is the base of horse pasture. I could see putting a berm in the pasture that stops run off from going into this area when it's cleared out again but what other options should be considered to keep this accessible to horses? Gravel would probably just sink in and disappear, large rocks might work but most of the riprap is really pointed/sharp. Unless a barrier reef could be installed that allowed water to flow over but keep out creek silt/debris then sand would just wash away. Is there a liner or something that could be installed then gravel or rocks on top to keep the horses from sinking into the mud? Would love the end result to be a place where the kids/adults could enter to play in the summer so anything that involved making this more of a beach would be ideal.
Would love any thoughts, references, things-not-to-do....

Now pond question.... most I see are dank filled with algae... surely a pump system or plants for purifying (like they do for natural swimmingpools) can be installed into a new pond to keep it clear? I'd like to put a pond on my property and hoping to find someone with experience, not just someone that will dig a hole and leave me with problems. I've called a couple of companies but so far no references or sample ponds have been provided for me to see. Any helpful ideas or referrals? My property is in NC.

Creeks & ponds - question for anyone - put here because I have a ctl/mtl