AbstractUnderwater robotic systems have the potential to assist and complement humans in dangerous or remote environments, such as in the monitoring, sampling, or manipulation of sensitive underwater species. Here we present the design, modeling, and development of an underwater manipulator (UM) with a lightweight cable‐driven structure that allows for delicate deep‐sea reef sampling. The compact and lightweight design of the UM and gripper decreases the coupling effect between the UM and the underwater vehicle (UV) significantly. The UM and gripper are equipped with force sensors, enabling them for soft and sensitive object manipulation and grasping. The accurate force exertion capabilities of the UM ensure efficient operation in the process of localization and approaching reef samples, such as the corals and sponges. The active force control of the tendon‐driven gripper ensures gentle/delicate grasping, handling, and transporting of the marine samples without damaging their tissues. A complete simulation of the UM is provided for deriving the required specifications of actuators and sensors to be compatible with the UVs with a speed range of 1–4 Knots. The system's performance for accurate trajectory tracking and delicate grasping of two different types of underwater species (a sponge skeleton and a Neptune's necklace seaweed) is verified using a model‐free robust‐adaptive position/force controller.