Short answers, pulled from the story.
The Pesse canoe, found in the Netherlands, is the oldest recovered boat in the world. It is a dugout made from the hollowed trunk of a Pinus sylvestris and was constructed somewhere between 8200 and 7600 BC. The canoe is exhibited in the Drents Museum in Assen, Netherlands.
A boat obtains its buoyancy by having most of its structure exclude water with a waterproof layer, such as the planks of a wooden hull or a hide covering. A raft is buoyant because it joins components that are themselves buoyant, such as logs or bamboo poles, and waves can pass up through it. This flow-through design makes rafts impractical in cold regions, where users face risk of hypothermia.
Fiberglass boats became popular around the mid-1960s, especially for recreational use. Known as GRP in the United Kingdom and FRP in the United States, fiberglass does not rust, corrode, or rot, though it can degrade from sunlight and temperature extremes over time.
Since 1998, the EU's Recreational Craft Directive defines four classes for leisure boats between 2.5 and 24 metres. Class A permits navigation in any waters. Class B is limited to offshore use with winds up to Force 8 and waves up to 4 metres. Class C covers inshore coastal navigation with winds up to Force 6 and waves up to 2 metres. Class D is restricted to rivers, canals, and small lakes with winds up to Force 4 and waves up to 0.5 metres.
The Plimsoll line is a marking on a ship's hull indicating the maximum safe loading level. It was introduced because commercial vessels must be correctly loaded to remain safe, and seawater in brackish areas such as the Baltic provides less buoyancy than open ocean saltwater, increasing the risk of overloading.
WH Mullins produced steel boats of galvanized iron from 1895 and by 1930 had become the world's largest producer of pleasure boats. Mullins also offered aluminum boats from 1895 through 1899 and again in the 1920s, making the company an early pioneer in both steel and aluminum recreational boat production.