Abstract: Recessed bottom tankers. Vessels described herein are built or retrofitted with side ballast tanks and optional forward bulbs extending to a level below the level of the vessel's cargo compartment to protect the cargo in case of collision or grounding. When compared to a double-hull or mid-deck design, the devices disclosed herein will considerably reduce the cost of a new tanker construction and make the retrofitting of some old single-hull ships economically acceptable. Furthermore, ballast tanks and bulbs designed in accordance with the present invention greatly reduce the possibility of ballast contamination and the risk of explosion due to oil leakage into ballast spaces as in double-hull designs.