The mighty Mekong is home to as many as 1,000 Irrawaddy dolphins - unique among cetaceans because their heads are rounded, and their beaks are short - but only 92 are left in a small section of the river between the town of Kratié (pop. just over 38,000) with its French-colonial-era architecture and the border with Laos. Most visitors take boat excursions, but stand-up paddleboarding is a wonderful way to spot this critically endangered species; explore remote river beaches and flooded forests; and meet with locals. Supasia offers various paddleboarding tours based out of Kratié, which is just under four hours by car north of capital Phnom Penh and six from Siem Reap.

Read about the other four here.