The invention discloses a moonpool, a maritime device with the same, and a sliding device arranged on the moonpool. Through respectively correspondingly forming second spaces on two side edges of thelength direction of a first space of a moonpool, width of the moonpool is increased on the position where the second space is formed, so that a maximum operation dip angle of a water-insulating casingpipe on the moonpool of the structure is increased. A swing region of the water-insulating casing pipe when the water-insulating casing pipe works normally is increased, and probability that the water-insulating casing pipe would strike the edge of the moonpool caused by storms when the water-insulating casing pipe swings is reduced, so that the water-insulating casing pipe can be adapt to requirement of a maritime device in adverse sea conditions. Occupation area of the second space is relatively low, and stability of the integrated structure of the maritime device is not influenced. The maritime device using the moonpool is arranged on the sliding device on the moonpool, and the maritime device also has the above advantages.