The present invention relates to a semisubmersible, cylindrical net cage (1) including two closable fixed bulkheads and a sliding bulkhead (9) extending in a radial direction from a central column (6) to a circumference, the sliding bulkhead (9) being rotatable about the central column (6). A bottom (14) that can be elevated is provided between the two closable fixed bulkheads. Also claimed is a closable bulkhead for a net cage (1), as well as a bottom (14) for the net cage that can be elevated.