Is that 500kg mass or negative buoyancy? Because 500kg of octogen (density of 1.91g/cm³) which thus would take up 261800cm³. An item of that volume and mass wou

Is that 500kg mass or negative buoyancy? Because 500kg of octogen (density of 1.91g/cm³) which thus would take up 261800cm³. An item of that volume and mass would only be 230kg negatively buoyant in sea water. Still very heavy, but basically neutral with 2 large lift bags (you can easily find 150kg pyramid lift bags for about 1-200€ each).