1. Determine the change in height:

* The swimmer falls 5 meters from the tower and then another 1.9 meters into the water.

* Total change in height (distance) = 5 m + 1.9 m = 6.9 m

2. Calculate the potential energy lost:

* Potential energy (PE) = mgh, where:

* m = mass (67 kg)

* g = acceleration due to gravity (9.8 m/s²)

* h = change in height (6.9 m)

* PE = (67 kg) * (9.8 m/s²) * (6.9 m) ≈ 4580 J (Joules)

3. Determine the work done by the water:

* Since the swimmer comes to a stop, all the potential energy is converted into work done by the water to stop the swimmer.

* Work (W) = PE = 4580 J

4. Calculate the net force:

* Work (W) = Force (F) * Distance (d)

* F = W / d

* F = 4580 J / 6.9 m ≈ 664 N (Newtons)

Therefore, the net force exerted on the swimmer by the water is approximately 664 N.

Important Note: This calculation assumes that all the potential energy is converted into work done by the water. In reality, some energy would be lost due to factors like friction and heat.