Answer:
8.67807 N
34.7123 N
Explanation:
m = Mass of shark = 92 kg
= Density of seawater = 1030 kg/m³
= Density of freshwater = 1000 kg/m³
= Density of shark = 1040 kg/m³
g = Acceleration due to gravity = 9.81 m/s²
Net force on the fin is (seawater)

The lift force required in seawater is 8.67807 N
Net force on the fin is (freshwater)

The lift force required in a river is 34.7123 N