| PUTUMAYO | River also known as the Rio Ica forming most of the border of Colombia with Peru |
| PILCOMAYO | Chief western tributary of the Paraguay River, forming most of the border between Paraguay and Argentina (9) |
| TAMAR | River in South West England, forming most of the border between Devon and Cornwall (5) |
| MEKONG | SE Asia's longest river, forming most of the border between Thailand and Laos (6) |
| NYASA | Third-largest and second-deepest lake of Africa, forming most of the eastern border of Malawi with Tanzania and Mozambique (5) |
| STOUR | River of East Anglia forming most of the county boundary between Suffolk and Essex (5) |
| YALU | River of eastern Asia forming most of the natural boundary between China and North Korea (4) |
| CONGO | River, also known as the Zaire, commonly considered the secondlongest in Africa (5) |
| URAL | River also known as the Yaik which runs through Russia and Kazakhstan (4) |
| LETICIA | Colombian town where the borders of Colombia, Brazil, and Peru meet (7) |
| ACRE | Unit of land equal to 4,840 square yards; or, a Brazilian state on the border with Peru, capital Rio |
| LAPAZ | Capital and largest city of Bolivia, in the west near the border with Peru (2,3) |
| THAMES | River also known as the Isis within Oxford's boundaries (6) |
| CAM | East Anglian river also known as the Granta (3) |
| YANGTZE | Longest Asian river also known as the Chang Jiang |
| DERWENT | Tasmanian river also known as timtumili minanya |
| SPEECHTHERAPIST | ICA thesp suffering with herpes with little time to see with little time to see diction specialist (6,9) |
| ORINOCO | What river is a border of Colombia and Venezuela? (7) |
| ARAL | Inland sea that forms part of the border of Kazakhstan |
| ODER | Part of the border of Brandenburg |
