Because the island on which the castle was erected is separated from the shore by at least two bodies of water, artificial defences such as moats or shield walls were usually unnecessary if the castle was surrounded by flowing water.
Karena pulau tempat puri berdiri dipisahkan dari daratan oleh sekurang-kurangnya dua macam perairan, maka struktur pertahanan buatan seperti parit atau tembok perisai biasanya tidak diperlukan jika puri dikelilingi air mengalir.