Try an anchor wizard: https://www.amazon.com/Anchor-Wizard-Kayak-Anchoring-System/dp/B01A5WG6UK/ref=sr_1_2?crid=3VU40Z3HBO5JU&dchild=1&keywords=anchor%2Bwizard&qid=1627459052&sprefix=anchor%2Bwiz%2Caps%2C221&sr=8-2&th=1
With a mushroom anchor 8 pounds should do it: https://www.amazon.com/Attwood-9941B1-Mushroom-8-Pounds-Aluminum-Plated/dp/B0000AY6ZX/ref=sr_1_6?crid=2XVNQF9DBL3JO&dchild=1&keywords=mushroom+anchor+8+lb&qid=1627459129&sprefix=mushroom+anchor%2Caps%2C237&sr=8-6