Boat
Differentiation from other prehistoric watercraft

The earliest watercraft are considered to have been rafts. These would have been used for voyages such as the settlement of Australia sometime between 50,000 and 60,000 years ago.

A boat differs from a raft by obtaining its buoyancy by having most of its structure exclude water with a waterproof layer, e.g. the planks of a wooden hull, the hide covering (or tarred canvas) of a currach. In contrast, a raft is buoyant because it joins together components that are themselves buoyant, for example, logs, bamboo poles, bundles of reeds, floats (such as inflated hides, sealed pottery containers or, in a modern context, empty oil drums). The key difference between a raft and a boat is that the former is a "flow through" structure, with waves able to pass up through it. Consequently, except for short river crossings, a raft is not a practical means of transport in colder regions of the world as the users would be at risk of hypothermia. Today that climatic limitation restricts rafts to between 40° north and 40° south, with, in the past, similar boundaries that have moved as the world's climate has varied.
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