An unmanned vehicle configured to selectively operate on at least a substantially planar water surface and while at least partially submerged in water, the unmanned vehicle comprising: a vehicle body comprising a pair of substantially parallel sponsons coupled together on opposite sides of a recessed well deck in a stern portion of the vehicle body, the recessed well deck being configured to stow a payload; a propulsion system carried by the vehicle body and configured to prope the unmanned vehicle; a maneuvering system carried by the vehicle body and configured to maneuver the unmanned vehicle; a vehicle control system carried by the vehicle body and configured to control a speed, an orientation, and a direction of travel of the unmanned vehicle in combination with the propulsion system and the maneuvering system a buoyancy control system carried by the vehicle body and configured to control buoyancy of the unmanned vehicle; a sensor system carried by the vehicle body and comprising a plurality of environmental sensors configured to sense environmental and operational characteristics for the unmanned vehicle; and at least one power supply carried by the vehicle body and configured to provide power to the propulsion system, the maneuvering system, the vehicle control system, the buoyancy control system, and the sensor system; wherein the vehicle control system, the buoyancy control system and the sensor system define a well deck positioning control system configured to launch and recover objects (3606, 3608) of the payload to/from the water while the well deck is at least partially submerged in water; wherein the buoyancy control system comprises ballast containers positioned within portions of the vehicle body, and a pump and valve system configured to vary amounts of water and air in the ballast containers and the recessed well deck; wherein the recessed well deck comprises a payload securing system wherein the plurality of environmental sensors of the sensor system at least include water level sensors configured to sense water levels in the ballast containers and the recessed well deck, and payload position sensors configured to sense the position of the payload relative to the payload securing system and the recessed well deck; and wherein the well deck positioning system further comprises a well deck positioning controller configured to provide output signals to the buoyancy contro system in response to input signals from the sensor system and at least one of operator instructions and autonomous operation instructions. a vehicle body comprising a pair of substantially parallel sponsons coupled together on opposite sides of a recessed well deck in a stern portion of the vehicle body, the recessed well deck being configured to stow a payload; a propulsion system carried by the vehicle body and configured to prope the unmanned vehicle; a maneuvering system carried by the vehicle body and configured to maneuver the unmanned vehicle; a vehicle control system carried by the vehicle body and configured to control a speed, an orientation, and a direction of travel of the unmanned vehicle in combination with the propulsion system and the maneuvering system a buoyancy control system carried by the vehicle body and configured to control buoyancy of the unmanned vehicle; a sensor system carried by the vehicle body and comprising a plurality of environmental sensors configured to sense environmental and operational characteristics for the unmanned vehicle; and at least one power supply carried by the vehicle body and configured to provide power to the propulsion system, the maneuvering system, the vehicle control system, the buoyancy control system, and the sensor system; wherein the vehicle control system, the buoyancy control system and the sensor system define a well deck positioning control system configured to launch and recover objects (3606, 3608) of the payload to/from the water while the well deck is at least partially submerged in water; wherein the buoyancy control system comprises ballast containers positioned within portions of the vehicle body, and a pump and valve system configured to vary amounts of water and air in the ballast containers and the recessed well deck; wherein the recessed well deck comprises a payload securing system wherein the plurality of environmental sensors of the sensor system at least include water level sensors configured to sense water levels in the ballast containers and the recessed well deck, and payload position sensors configured to sense the position of the payload relative to the payload securing system and the recessed well deck; and wherein the well deck positioning system further comprises a well deck positioning controller configured to provide output signals to the buoyancy contro system in response to input signals from the sensor system and at least one of operator instructions and autonomous operation instructions.