I am unsure of how to answer this completely, but I will give it my best.
It could be meant that there is no physical boundary holding them apart and that the world's oceans simply flow into each other rather than being separated. Such as the pacific and Atlantic. They are not held apart, they flow around countries and flow into each other at a certain point.
Explanation:
Ocean currents act much like a conveyor belt, transporting warm water and precipitation drom the equator toward the poles and cold water from the poles baxk to the tropics . Thus, ocean currents regulate global climate, helping to counteract the uneven distribution of solar radiation reaching Earth's surface
Answer:
Wind causes surface ocean currents. The wind direction also helps determine the currents.
We can look at this from two perspectives, the affect on the physical features of the native people in this region, and the ethnic composition and foreign influence on it.
1. The physical features of the people are heavily affected by the environment, the skin is very resilient to sunlight due to the higher UV received in the high altitudes, the nose is bigger and wider for better and easier intake of oxygen which is more sparse in here, people are shorter and stockier for better bearing of the low temperatures and lower nutrition, the lungs capacity is higher etc.
2. The ethnic composition is relatively homogeneous, the mixing with the newcomers had been small, so these people had kept their native ethnic core due to the harsh region which has been evaded by the newcomers.