The ocean is a harsh and unstructured environment for robotic systems; high ambient pressures, saltwater corrosion and low-light conditions demand machines with robust electrical and mechanical parts that are able to sense and respond to the environment. Prior work shows that the addition of gentle suction flow to the hands of underwater robots can aid in the handling of objects during mobile manipulation tasks. The current paper explores using this suction flow mechanism as a new modality for tactile sensing; by monitoring orifice occlusion we can get a sense of how objects make contact in the hand. The electronics required for this sensor can be located remotely from the hand and the signal is insensitive to large changes in ambient pressure associated with diving depth. In this study, suction is applied to the fingertips of a two-fingered compliant gripper and suction-based tactile sensing is monitored while an object is pulled out of a pinch grasp. As a proof of concept, a recurrent neural network model was trained to predict external force trends using only the suction signals. This tactile sensing modality holds the potential to enable automated robotic behaviors or to provide operators of remotely operated vehicles with additional feedback in a robust fashion suitable for ocean deployment.