To provide an in-liquid observation apparatus capable of clearly and easily observing sea water even if fluctuation occurs in a portion near a surface of a seawater surface.SOLUTION: The in-liquid observation device comprises a tubular member whose top and bottom are opened, a bottom member attached so as to close the bottom opening of the tubular member, a floating member on the liquid surface of the tubular member, And a communicating member for communicating the space between the bottom member and the floating body and the outside of the tubular member. The bottom member and the floating body are at least partially transparent so that the object can be seen through the bottom opening from the top opening side of the tubular member.BACKGROUND OF THE INVENTION【課題】 海水面の表面近くの部分において揺らぎが生じていても海水中を明瞭かつ容易に観察することができる液中観察装置を提供する。【解決手段】 液中観察装置は、頂部及び底部が開放された筒状部材と、筒状部材の底部開口を塞ぐように取り付けられた底部材と、液体の液面上に浮き、筒状部材の内部を上下に移動可能な浮体と、底部材及び前記浮体の間の空間と筒状部材の外部とを連通する連通部材とを備える。底部材及び浮体は、筒状部材の頂部開口の側から底部開口を介して物体が見えるように少なくとも一部が透明に構成されている。【選択図】 図1
