What makes two boats collide when the space through which a fluid flows becomes narrow?

When the space through which a fluid flows narrows, it can increase the fluid's velocity due to the principle of continuity, leading to changes in pressure. This alteration in flow dynamics can create turbulence or eddies that affect the boats' movement. If both boats are navigating the same narrow passage, the increased speed and unpredictable flow patterns can cause them to collide as they struggle to maintain their course. Additionally, any sudden changes in direction or speed can exacerbate the risk of collision.