Answer: yes
Explanation: Assuming a it's moving 20m/s in the west direction and slowing down at a rate of -5m/s² (deceleration), the negative sign would imply the westward direction because -5 west is the same thing as +5 east. So, the boat is moving 20m/s west direction and accelerating at 5m/s² east direction.
Other examples of these are: Cars and and tricycles.