3 days is much needed to visit the whole of beach City, coastal city Vishakapatnam. I will share some offbeat spots see if it is useful for your travel.
Duduma falls
Deomali
Revupolavaram beach
Bojjannakonda
Lingalakonda
Kondakarla Ava.
https://tripoto.page.link/UqXhWEEGSEFhxkW78
Kindly check the above Tripoto link for more details.