The colour of the water and sand varies from beach to beach, and depending on the time of the day as well, as the "temperature" of the light changes affecting the perceived colour of things, but in general it has a beautiful colour, but not white sands as in Cancun.
As for activities, Cabo is the place, you can find countless ATVs, buggies, canopy zip lines, bungee jumping, helicopter tours, boat tours, swimming with dolphins, horseback ridding, snorkeling tours, diving, deep sea fishing, whale watching, sightseeing tours, parasailing, 4x4 tours, rhino tours, off-road tours.... and it goes on and on.
You couldn't have made a better choice in my opinion.