Start your trip by exploring the INS Kurusura submarine museum. The museum is located in the Rama Krishna mission beach and gives the visitors a chance to see and understand the working of an actual submarine. Inside, you will see the control room, sonar equipment, and torpedo rooms along with detailed information about the submarine's history and usage. You can also take a walk around the beach and have a quick snack from the stalls nearby.
The next day, head to Simhachalam temple, which has been an important pilgrimage centre for Vaishnavites since the 9th century. The temple is located on a hill and is a perfect place for a spiritual retreat. Built-in the Kalinga style of architecture, the temple is known for its rich carvings and beautiful paintings. You can take a tour of the temple and also interact with the local priests who will explain the significance of various rituals. Do not forget to try the famous prasadam served at the temple.
If you have an extra day in Vishakapatnam, you can explore other places such as Rishikonda beach, The Kailasagiri park or Kambalakonda wildlife sanctuary.
On the other hand, if you have less time, you can skip either INS Kurusura submarine museum or Simhachalam temple.