Islands are used for mining of minerals, and other useful stuff. The comprehensive list of which can be seen here.
Possibility of being combined with the Beach terrain in sea areas
Caves and exploration areas
Various event hosting platforms
Map will end by endless sea and storm weather
Whatever one wishes to do in real life in the waters, water sports, exploration, or any other experience, but is too afraid to do or cannot do due to the physical constraints, they can do in the beach terrain in the metaverse.