Lara will need it to get through the Icy Water which would otherwise freeze her to death. She can jump ashore from within the boat. From the boat you can also reach from the water inaccessible areas like the second Secret in this level.
The Inflatable Boat is yellow with black and red markings and has a grey Outboard motor on which the number 2001 (back) and the name Croft (side) can be found in mint green colour. On the front of the boat the number 993 is printed twice in black letters.