Oxygenating pond weed (Camborne TR14)

The grandchildren have helped turn a paddling pool into a little pond, I bought a couple of suitable marginal plants to make it look nice (!) but the local garden centres have run out of oxygenating plants so the water is pretty murky. Does anyone have a pond with suitable surplus weed to share? Happy to collect within 10 ish miles of Camborne... thank you for reading!