I have used those in a lake for a pontoon, 16 pound ones in the past and they work fine in a mud bottom. Mine were stolen a few years back and I replaced them with 16 pound sledge hammer heads from a flea market. lolol and no one has stolen those yet
We are o the Tennessee river and it is mostly mud or sandy bottom. I use it in the river on occasion and also when I park the boat on the bank. I tie the front off and then throw the anchor out behind the boat or just up stream to keep it from floating around against the bank.