noun which may take the genitive case particle 'no', noun
on the water; waterborne; aquatic
Often used before の or in compounds for activities, transport, police, sports, and facilities that operate on the surface of water.
水上バスで川を下った。
We went down the river by water bus.
夏は湖で水上スポーツを楽しむ人
In summer, many people enjoy water sports on the lake.
noun
A less central noun use referring to the area at or by the water; in modern everyday Japanese, 水辺 or 水際 is usually clearer for this meaning.
「水上」は文脈によって、水辺や水際を指すことがある。
Depending on the context, 水上 can refer to the waterside or water's edge.