You can trek, go fishing, go birding, go see some wildlife within 25 Km radius
This fort is in the middle of the sea and takes you back in time. The boat ride is very adventurous. You have to Rs 50 per person. These boats have the most primitive way of sailing, they sail with the direction of the wind. The sea was a lil choppy when we stepped into the boat and the struggle of the 4 boatmen to find the right direction was a thing to see. The fort was visible at a distance. It's magnanimous. I was in Rome sometime back and the Colosseum had given me the same feeling. It's a pity that the government does nothing to protect these ancient monuments.
The boatmen tell you mesmerizing stories of shivaji and the fort on the way. It takes about half an hour to reach the fort. Inside the fort it's all ruins and thick jungle. You can hire a guide for 300 bucks who will show you around but it's not worth and you may want to look around a bit by yourself. On the top of the fort you can still see some canons that look out to the sea. I sat by them and thought how many enemy ships must have been bombarded by these canons!