Comprising 15 islands of mangrove creeks, tropical rainforest and reefs supporting 50 types of coral and plenty of colourful fish, the 280-sq-km Mahatma Gandhi Marine National Park is ideal for snorkelling (gear rental ₹300). Three boats depart on half-day trips from Wandoor Jetty from 7.30am depending on demand, costing ₹885 in addition to the permit (Indian/foreigner ₹75/1000) you'll need to prearrange from Port Blair's tourist office up to three days ahead. No plastics allowed.
The marine park’s snorkelling sites alternate every six months between Jolly Buoy and Red Skin, allowing the other to regenerate.