Q.How can I cover the liner of my pond with plants
The pond is as deep as it will go but this leaves large amounts of liner showing. How can we hide the liner above the water line?
Generally rocks are used to anchor a pond liner and to create a natural ponding effect.
Here is where you can be creative with ground cover plants and perennials to create a lovely garden.
Here are some links to help you get started.
https://www.gardeningknowhow.com/garden-how-to/projects/how-to-build-a-small-pond.htm
https://www.gardeningknowhow.com/ornamental/water-plants/wgen/popular-pond-plants.htm