**Ratio of Person's Velocity to River Water Velocity**

To determine the ratio of the person's velocity to the river water velocity, we need to consider the situation where the person swims at an angle of 0° to the current of the river in order to meet a target on reaching the opposite point.

Let's break down the problem into smaller steps to understand it better:

1. **Understanding the Angle and Components**: When the person swims at an angle of 0° to the current, it means that the person is swimming directly across the river, perpendicular to the current. We can consider the velocity of the person and the velocity of the river water as vectors.

2. **Velocity of the River Water**: The velocity of the river water represents the speed and direction at which the river water is flowing. Let's assume that the velocity of the river water is v_r (magnitude) and it flows from left to right (positive direction).

3. **Velocity of the Person**: The velocity of the person represents the speed and direction at which the person is swimming. Let's assume that the velocity of the person is v_p (magnitude) and it is directed towards the opposite point of the river (from right to left).

4. **Vector Addition**: Since the person is swimming at an angle of 0° to the current, the person's velocity vector and the river water velocity vector are parallel to each other. In this case, we can add the two vectors to get the resultant velocity vector.

5. **Resultant Velocity**: When the person swims directly across the river, the resultant velocity vector will have the same magnitude as the person's velocity (v_p), but in the opposite direction of the river water velocity (from left to right).

6. **Ratio of Velocities**: The ratio of the person's velocity to the river water velocity can be calculated by dividing the magnitude of the person's velocity (v_p) by the magnitude of the river water velocity (v_r).

Thus, the ratio of the person's velocity to the river water velocity is v_p/v_r.

In conclusion, when a person swims at an angle of 0° to the current of the river, the ratio of their velocity to the river water velocity is v_p/v_r. This ratio represents the speed at which the person is swimming relative to the speed of the river water.