Question 55 GLI03 - Master-LT 500-1600 GRT

The Correct Answer is A **Explanation of why option A ("In all depths of water") is correct:** A vessel "squats" (i.e., experiences a reduction in under-keel clearance, or 'UKC', along with a change in trim—usually a stern-down trim) due to the hydrodynamic forces created by its movement through the water. This phenomenon is caused by the pressure changes around the hull as the water must accelerate past the vessel. While the *severity* of squat is dramatically increased in shallow water, the underlying hydrodynamic mechanism occurs in all depths of water, including deep water. Therefore, a vessel technically squats whenever it is moving through the water, regardless of depth. **Explanation of why each of the other options is incorrect:** * **B) Only when in narrow channels:** Squat is most *pronounced* in shallow and confined (narrow) waters because the restriction significantly accelerates the return flow of water, leading to a much greater pressure drop beneath the hull. However, squatting is not limited only to channels; it occurs whenever the vessel is moving. * **C) Only when in deep water:** This is incorrect. While squat does technically occur in deep water, it is typically negligible or very minor, especially at lower speeds. More importantly, excluding shallow water (where squat is most critical) makes this statement fundamentally false. * **D) Only when in shallow water:** This is incorrect. While shallow water is where the effect of squat becomes dangerous and most significant (the vessel may actually touch the seabed), the physical phenomenon of squatting is a basic hydrodynamic consequence of a vessel moving through water and is therefore present even in deep water.