Sennen Cove overlooks the 1 mile of sand on Whitesand beach, a family friendly beach, with a restaurant and kiosk. The beach is lifeguarded in the holiday season, with great bodyboarding waves; and good learner and experienced surfing. You can stretch out and swim, fly your kite, watch the plane going to the Scilly Isles and the lifeboat going out on a 'shout'. You may see dolphins, seals and basking sharks.
Gwynver beach, just across the headland has a great surf history and fantastic waves for experience surfers, and is dog friendly.
It's not far to drive to Porthcurno, another of my favourites. When the sea at Sennen is dramatic, it is often calmer around the headland. When the wind is onshore at Sennen its offshore at Porthcurno, so you can shelter there in a small bay with steep cliffs. Nearby is Treen, a cliff scramble to a sheltered cove with a nudist area at the far end (just so you know!).
I have wetsuits in the house which you can borrow if you don't have your own and want to give body boarding or surfing a try.
The best surf school in Sennen Cove is Sam Smart's Surf School - Smart Surf. The boys are pros, and they teach in small groups. You will be standing up on your board in your first lesson, and they are the best value for your money.