PROBLEM TO BE SOLVED: To allow adhesion of spores to a water-permeable case itself and to also allow fixation of seaweed, in the water-permeable case that is a constituent element of an artificial fish reef or an artificial seaweed bed.SOLUTION: A water-permeable case 1 is a container having water-permeable faces in a part or in the whole and is filled with shells thereinside. In the water-permeable face, crosspieces 211, 221 and 311 surrounding water-permeable holes 212, 222 and 312 are formed with projecting stripes 213, 223 and 313, and level difference parts 214, 224 and 314 are configured between the crosspieces 211, 221 and 311 and the projecting stripes 213, 223 and 313. Thereby, the water-permeable case 1 has effect of making spores adhere and fixing seaweed by presence of the level difference parts 214, 224 and 314.
