The five major beaches of Gokarna are Gokarna main beach
Half moon beach and paradise beach. There are some things to do in these beaches which I will share see if it is helpful. Beach Trek on these beaches is popular
You could camp at paradise beach where kayaking is a part
Surfing for beginners is taught in beaches if Gokarna
You could witness shore lines in the night via bio-luminescence. On full moon day nights every beach gives you silver lining. Unique thing is if you are lucky you could spot Dolphins especially in Om and half moon beaches.
Kindly check the above link for more details.