A motor ship in a collision with a boat can sink it without any damage to itself. How does this fit with Newton’s 3rd Law?

From Newton’s third law it follows:
M1 / m2 = -a2 / a1, M1 and m2 are the body masses of the motor ship and the boat, respectively, and a1 and a2 are the acceleration of the motor ship and boat, respectively, after the collision.
From this it can be seen that the accelerations of bodies after interaction are directed in opposite directions and the less the mass of the body, the greater its acceleration.
The mass of the boat is much less than the mass of the motor ship.
Therefore, colliding with a motor ship, the boat gets acceleration in the direction of the ship’s movement and may well turn over and sink.
At the same time, the motor ship receives the least damage.