The speed of the water between the ships will be higher, causing them to be pushed closer together.
Work Step by Step
Some water is pulled alongside the ships at high speed. The water between the closely-aligned ships, being dragged by both vessels, moves faster than the water to the left and right (i.e., port and starboard) of the two ships. By Bernoulli’s principle, the faster-moving water between the ships is at a lower pressure than the water outside of the ships. The pressure difference applies a force on the ships that tends to push them closer together.