A 21st century boom in underwater technologies that has made it more readily possible to identify and recover sunken vessels and their contents has also created an urgency to assign title over cargo originating in former colonies, that sank aboard colonial vessels and that has been partially or totally under water, periodically or continuously, for at least 100 years (“UCH-cargo”). This has raised prominent and complex questions over these objects, namely, what belongs to who and how. It has also resultantly spurred a race to a pot of riches under the water, but without a competent legal mechanism to tame it, or to reconcile laws assigning title over the UCH-cargo with the socio-political and humanitarian shifts that occurred since it sank. To fill these lacunae in the lex lata, this dissertation identifies legal principles to determine title and define proprietary rights over UCH-cargo. Originating centuries ago when identifying and recovering sunken cargo seemed as implausible as, until recently, identifying and recovering space materials, existing laws available to adjudicate disputes emerging from such discoveries are, to say the least, incompatible and generally undefined. Even significant international conventions abstain from providing guidance on determining title and they, together with domestic laws, provide for either unlimited or overly limited proprietary rights over it. This dissertation defines and analyzes, within the current regime, three stages in a legal and ethical conundrum of UCHcargo disputes. It proposes the development of laws, consistent with modern legal and ethical principles, that could uniformly adjudicate contending claims when contemporarily discovered UCH-cargo is brought before modern courts. This dissertation also proposes a reconfigured framework for proprietary rights over these objects that could prevent the perpetuation of past injustices, halt unjust enrichment and better ensure their protection and preservation for the benefit of mankind as a whole.