Locomoting in the surf-zone is a challenge for traditional robots, as they must be able to resist hydrodynamic forces of waves while overcoming the challenges of walking on sand, a granular media. Taking inspiration from live crabs that can navigate the surf zone efficiently, we demonstrate that inward gripping with crab-inspired curved dactyls on a crab-like robot can increase its effective weight underwater, which is the weight of the robot minus the buoyancy force, to better resist wave forces. Gripping can also reduce the cost of transport and allow for more efficient operation in a lab-created surf-zone environment. Six different walking gaits are tested on an 18 degree-of-freedom crab-inspired hexapod robot. The tests are conducted on sand underwater, with and without the presence of waves. Results show that the gait with a smooth swing path combined with front only gripping is on average 50% more energy efficient than the gait with a polygonal swing path with front and rear gripping in still water and 29% more energy efficient in waves.