A　water　hydraulic　flexible　gripper　with　three　flexible　actuators　is　proposed,　which　integrates　a　soft　external　skin　and　a　flexible　inner　skeleton　to　enhance　resistance　against　water　pressure.　To　investigate　the　deformation　characteristics　of　the　water　hydraulic　flexible　actuator,　a　mathematical　model　is　established　to　describe　the　relationship　between　water　pressure　and　actuator　deformation.　The　effects　of　different　materials,　structural　sizes,　and　inlet　pressure　are　analyzed　through　simulation.　A　Kriging　model　is　utilized　to　fit　the　simulation　results,　while　a　multi-island　genetic　algorithm　is　employed　to　obtain　an　optimal　solution　for　the　structure　of　the　flexible　actuator.　Finally,　the　deformation　of　the　flexible　actuator　under　various　inlet　pressures　is　quantified　through　experimental　measurements,　and　the　obtained　results　exhibit　degree　of　consistency　with　the　simulation　outcomes.　After　completing　static　experiments　at　a　simulated　sea　depth　of　1000　m,　the　tip　forces　of　flexible　actuators　were　tested,　and　then　land　and　underwater　grasping　experiments　were　conducted.　The　water-hydraulic　flexible　actuator　developed　in　this　study　has　great　potential　for　handling　fragile　or　deformable　objects　during　deep-sea.　This　promotes　the　application　of　water-hydraulic　flexible　manipulators　in　the　field　of　underwater　robotics,　providing　higher　flexibility　and　adaptability　compared　to　traditional　rigid　manipulators.　©　2024　Elsevier　B.V.