It is conservative to assume that all sunk biomass is remineralized and that ocean circulation and currents will eventually return the CO₂ back to the surface ocean, where it will be brought into equilibrium with the atmosphere. The estimated timescale of this ventilation is dependent on the location of sinking and depth achieved, which must be characterized at the project level but can be informed by models. Given these dynamics, any claim about the volume of total carbon removal facilitated by deepwater carbon storage should be accompanied by a clear claim about the associated time horizon of storage. Our uncertainty evaluation reflects the uncertainties associated with estimating carbon stored in the deep ocean for 1000+ years. Those interested storage on longer timescales may find it appropriate to adjust these uncertainties.