The best and the most exciting activity to experience in Grand Island, Goa is Scuba Diving. Grand Island is 25 kilometers from the main roads and will take about two hours for you to reach by boat. The sea is shallow(about 4-14m) for beginners. You face numerous marine species and creatures deep down the sea. For cheapest Malvan Beach is best as the cost of scuba diving is only INR 2500 and is cheaper than other places in Goa. Good Luck!!