Abstract: Unmanned marine devices require long-term autonomous operation, yet limited onboard energy storage remains a critical challenge. In-situ wave energy harvesting offers a promising solution, but conventional pendulum harvesters suffer from narrow frequency bandwidth and poor adaptability to irregular excitations and variable sea states. This work presents two novel pendulum-based designs to address these issues. First, a magnetic multi-stable pendulum harvester creates multiple potential wells to enhance broadband response under multi-directional irregular waves, significantly improving output performance compared to traditional designs. Second, an origami-inspired deformable pendulum harvester enables dual-mode operation, with a fully expanded state for normal energy harvesting and a fully folded state for protection in harsh sea conditions. The folding mechanism is actuated pneumatically with low pressure requirements. Both concepts are validated through analytical modeling, numerical simulation, and field experiments. The proposed designs substantially improve the adaptability and robustness of in-situ pendulum wave energy harvesters, offering practical pathways for powering unmanned marine devices in diverse ocean environments.