with two long beaches, all together, 5 km of sand and water, both, on summer months anyway, offers, lots and all kind of water sports. sailing, canoeing, water bikes and so on.
you'll find no cause for doing nothing.
along with parasailing,
ride an helicopter for the best overviews of Benidorm and its unique skyline,
and many others radical sports.
You can learn to waterski in Benidorm. Since 1966 the cable ski of Brnidorm already exists. I must say that I've never tried it.