You are at a UK port. The vessel is loaded to the summer load line. Your examiner asks: "What determines the summer load line, what are the different zones, and what is the consequence of overloading beyond the assigned load line?"

A. The summer load line is determined by the ICLL 1966 (International Convention on Load Lines) as implemented by the MCA under the Merchant Shipping (Load Line) Regulations 1998. Zones: Tropical (T), Summer (S), Winter (W), Winter North Atlantic (WNA), Tropical Fresh Water (TF), Fresh Water (F). Overloading beyond the assigned load line is a criminal offence under the Merchant Shipping Act 1995, and the vessel may be detained by PSC. The master and shipowner may face prosecution and unlimited fines.

B. The summer load line is set by the ship's classification society at each annual survey based on the current cargo capacity. The zones are: Summer, Winter, and Arctic.

C. Overloading beyond the load line is a civil matter only. PSC cannot detain a vessel for a load line violation — they can only issue an advisory notice.

D. Load line zones only apply in international waters. In port and inland waters, the load line is advisory only and the master may exceed it at their discretion.

A. GM (metacentric height) is the distance between the centre of gravity (G) and the metacentre (M). A positive GM (M above G) indicates stable equilibrium — the vessel will right itself when heeled. A very low GM risks loll, slow period of roll, and potential capsize. A very high GM (stiff ship) causes a rapid, violent rolling motion that can create excessive dynamic loads on cargo, structures, and crew — which can be as dangerous as low stability.

B. GM is always a positive value. A negative GM means the ship is overloaded and must discharge cargo immediately.

C. GM is the distance between the keel and the metacentre. A higher GM always means a safer, more stable vessel regardless of its magnitude.

D. GM only applies to loaded conditions. In ballast, stability is assessed using only the KG value.

A. Key GZ curve features: range of stability (angle at which GZ returns to zero); maximum GZ and angle of maximum GZ; area under the curve (dynamical stability). IMO IS Code 2008 criteria: area 0-30 degrees minimum 0.055 metre-radians; area 0-40 degrees (or to flooding angle if less than 40) minimum 0.090 metre-radians; area 30-40 degrees minimum 0.030 metre-radians; maximum GZ at least 0.200 metres at 30 degrees or greater; initial GM not less than 0.150 metres.

B. The minimum GM under all criteria is 0.5 metres. The GZ curve must reach a maximum of at least 0.5m at any angle between 20 and 60 degrees.

C. The only IMO requirement is that the angle of vanishing stability must exceed 60 degrees. Area under the curve and initial GM are national flag state requirements only.

D. The IMO IS Code applies to new vessels only. Older vessels built before 2010 comply with the 1966 Load Lines convention stability requirements only.