Off-Shore Vessels.  Easily recognised by their large flat cargo carrying platform aft built specifically to service oil rigs.  The more powerful vessels are described as Anchor Handling vessels and as such can sometimes double as tugs. Cruise/Passenger Liners.  The glamour vessels of the oceans nowadays designed with short 7-14 day voyages in mind with as many ports of call as possible inserted into the schedule.  They are usually of a very shallow draft, which enables them to enter or get as close as possible to as many exotic ports as possible. Ferries.  Designed to ply between the same two ports as quickly as possible and as often as is economically viable.  They are almost all Ro/Ros (with the occasional train ferry) and are designed for the rapid loading/unloading of the passengers, cars and lorries.  They range in size from the super ferries with facilities which would not shame a cruise liner (in fact some ferries advertise themselves as mini cruises) down to the humble cross river or harbour ferry. Laker. A vessel capable of trading into the Canadian/USA Great Lakes where there is a beam restriction in the St. Lawrence Seaway locks of 23.15m and a draft restriction of 26ft. Fresh Water (up to about 30,000 dwat part loaded because of the draft limitation to about 19,000 dwat). Panamax.  A large vessel capable of transiting the Panama Canal where there is a beam restriction of 32 metres and a draft of about 12 metres Fresh Water (variable) – (about 70,000 dwt part loaded to about 55,000 dwt because of the draft limitation). Aframax.  Now loosely applied to tankers just under 80,000 dwt.  Its origins go back to a committee formed at the behest of the major oil companies called The London Tanker Brokers Panel which periodically calculated Average Freight Rate Assessments (AFRA).  These rates were used for a variety of purposes even including long term contracts in which the parties agreed to relate the freight rate to the current AFRA in some way. One category of size for which an AFRA was calculated was 45,000 to 79,999 and there was a big drop in rate after that for the 80,000 to 159,999 size.  It was, therefore, sensible for owners having ships built of around 80,000 to ensure that, in fact, they did not exceed 79,999.  The Panel still exists but is now independent of the oil companies and it calculates AFRAs commercially for anyone wishing to use the service.