Floating net-rafts 1. are primarily used in Japan 2. are limited by sea bottom 3. can only enclose small areas 4. All of the above

Floating net rafts are primarily used in the japan. They are limited by sea bottom and it can only enclose small areas.

Explanation:

These floats are first used by fishermen all over the world to keep their net which was used for fishing. It expands its lifetime without getting damaged. It is a popular collector's item. These floating rafts avoid large groups of fishing nets to stuck together. This ball creates a buoyancy force that contains air inside it. Nowadays it wasn't used by the fishermen but it is still floating in the oceans in large numbers.