A floating alternative for preserving Mikasa

If Japan knew a dry concrete berth would harm Mikasa, how could it preserve the ship while satisfying treaty limits?

Japan could immobilize Mikasa inside a cofferdam or enclosed pool, but it would need continuous water-quality and corrosion management.

Mikasa would probably remain at the same site, inside a massive cofferdam that prevented movement while leaving the hull afloat. The proposal assumes that Japan would negotiate a different treaty arrangement if it knew concrete would damage the ship. Keeping the enclosed water clean would then become a continuing maintenance task. Filtration or an exchange system with the nearby port could maintain circulation. Fresh water is also suggested as part of the arrangement.