Underwater wireless sensor systems, also known as UWSNs, are a laudable, recently developed, and game-changing discovery that finds a number of uses in oceanographic research. An underwater wireless sensor network gives a broad idea in utilization's and exploring of underwater resources. The Unmanned Underwater Sensor Network (UWSN) is comprised of a vast number of nodes that receive sensors and self-driving vessels that are transported to coordinate a group activity in the ocean. To accomplish this goal, sensor nodes and under water autonomous vehicles are self-organized in an independent system which can adjust to the characteristics of oceanic condition. But the unique characteristic of the submerged acoustic correspondence channel is completely different when compared to Terrestrial systems. Like harsh environment, acoustic correspondence channel, high error rates, propagation delays, mobility, low transmission and multipath effect capacity of water channels. The sensors that make up UWSN networks are often installed in the buoyant. Because of the properties of the ocean, buoyant nodes are particularly susceptible to attacks based on self-centered behaviour. The selfish behavioural attack causes the major problems in forwarding of data to the ship. So, it is very important to provide effective and reliable security mechanisms, to detect the selfish behavioural nodes and to provide secured routing to the ships. Entropy-based ACO algorithm is developed for optimal route selection. This study identifies the fundamental obstacles that need to be overcome in order to discover a secure and optimal path for navigation in UWSN. Entropy calculated based on the details that were supplied by the distinguish nodes in the water that measure things like the wind speed, temperature, and depth. This would be the major points to analyse in the ship movement based on the Pheromone level for the path available in the coverage from the ship. Pheromone level and route strength is assessed and ship is directed towards the optimal route.This security mechanism helps to identify the abnormal nodes and provides appropriate routing method.