Suiren-jo was a term used by people connected to traditional Japanese swimming, referring to separated areas of the sea, rivers, ponds or moats for learning to swim, and these were generally called 'suiei-jo' (swimming areas).
水練場とは、海、川、池や堀を区切った箇所で泳法を学ぶ場を日本泳法関係者が使った呼称であり、一般には「水泳場」と呼ばれていた。