Air draft (or air draught) is the distance from the surface of the water to the highest point on a vessel. This is similar to the "deep draft" of a vessel which is measured from the surface of the water to the deepest part of the hull below the surface, but air draft is expressed as a height, not a depth.  
The vessel's "clearance" is the distance in excess of the air draft which allows a vessel to pass safely under a bridge or obstacle such as power lines, etc. A bridge's "clearance below" is most often noted on charts as measured from the surface of the water to the under side of the bridge at the chart datum Mean High Water (MHW),   a less restrictive clearance than Mean Higher High Water (MHHW).
In 2014, the United States Coast Guard reported that 1.2% of the collisions it investigated in the recent past were due to vessels attempting to pass underneath structures with insufficient clearance. 
The Bridge of the Americas in Panama limits which ships can traverse the Panama Canal due to its height at 61.3 m (201 ft) above the water. The world's largest cruise ships, Oasis of the Seas, Allure of the Seas and the Harmony of the Seas will fit within the canal's new widened locks, but they are too tall to pass under the bridge, even at low tide (the two first ships are 72 m (236 ft), but do have lowerable funnels, enabling them to pass the 65-metre (213 ft) Great Belt Bridge in Denmark). New vessels are rarely built not clearing 65 m (213 ft), a height which accommodates all but the largest cruise and container ships.
The Suez Canal Bridge has a 70-metre (230 ft) clearance over the canal.
The Bayonne Bridge, an arch bridge connecting New Jersey with New York City, undertook a $1.7 billion modification to raise its roadbed to 66 m (217 ft). 
The Kiel Canal is a 98-kilometre-long (61 mi) freshwater canal in the German state of Schleswig-Holstein. The canal was finished in 1895, but later widened, and links the North Sea at Brunsbüttel to the Baltic Sea at Kiel-Holtenau. An average of 250 nautical miles (460 km) is saved by using the Kiel Canal instead of going around the Jutland Peninsula. This not only saves time but also avoids storm-prone seas and having to pass through the Danish straits.
The Panama Canal is an artificial 82 km (51 mi) waterway in Panama that connects the Atlantic Ocean with the Pacific Ocean and divides North and South America. The canal cuts across the Isthmus of Panama and is a conduit for maritime trade. One of the largest and most difficult engineering projects ever undertaken, the Panama Canal shortcut greatly reduces the time for ships to travel between the Atlantic and Pacific oceans, enabling them to avoid the lengthy, hazardous Cape Horn route around the southernmost tip of South America via the Drake Passage or Strait of Magellan and the even less popular route through the Arctic Archipelago and the Bering Strait.
Altitude or height is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context. Although the term altitude is commonly used to mean the height above sea level of a location, in geography the term elevation is often preferred for this usage.
Mean sea level (MSL) is an average surface level of one or more among Earth's coastal bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datum – a standardised geodetic datum – that is used, for example, as a chart datum in cartography and marine navigation, or, in aviation, as the standard sea level at which atmospheric pressure is measured to calibrate altitude and, consequently, aircraft flight levels. A common and relatively straightforward mean sea-level standard is instead the midpoint between a mean low and mean high tide at a particular location.
A waterway is any navigable body of water. Broad distinctions are useful to avoid ambiguity, and disambiguation will be of varying importance depending on the nuance of the equivalent word in other languages. A first distinction is necessary between maritime shipping routes and waterways used by inland water craft. Maritime shipping routes cross oceans and seas, and some lakes, where navigability is assumed, and no engineering is required, except to provide the draft for deep-sea shipping to approach seaports (channels), or to provide a short cut across an isthmus; this is the function of ship canals. Dredged channels in the sea are not usually described as waterways. There is an exception to this initial distinction, essentially for legal purposes, see under international waters.
A nautical chart is a graphic representation of a sea area and adjacent coastal regions. Depending on the scale of the chart, it may show depths of water and heights of land, natural features of the seabed, details of the coastline, navigational hazards, locations of natural and human-made aids to navigation, information on tides and currents, local details of the Earth's magnetic field, and human-made structures such as harbours, buildings, and bridges. Nautical charts are essential tools for marine navigation; many countries require vessels, especially commercial ships, to carry them. Nautical charting may take the form of charts printed on paper or computerized electronic navigational charts. Recent technologies have made available paper charts which are printed "on demand" with cartographic data that has been downloaded to the commercial printing company as recently as the night before printing. With each daily download, critical data such as Local Notices to Mariners are added to the on-demand chart files so that these charts are up to date at the time of printing.
The Bayonne Bridge is an arch bridge spanning the Kill Van Kull connecting Bayonne, New Jersey, with Staten Island, New York City. It carries New York State Route 440 (NY 440) and New Jersey Route 440. It is the sixth-longest steel arch bridge in the world, and it was the longest in the world at the time of its completion. The bridge is also one of four connecting New Jersey with Staten Island; the other two roadway bridges are the Goethals Bridge in Elizabeth and Outerbridge Crossing in Perth Amboy, and the rail-only span is the Arthur Kill Vertical Lift Bridge, all of which cross the Arthur Kill.
Panamax and New Panamax are terms for the size limits for ships travelling through the Panama Canal. The limits and requirements are published by the Panama Canal Authority (ACP) in a publication titled "Vessel Requirements". These requirements also describe topics like exceptional dry seasonal limits, propulsion, communications, and detailed ship design.
A cargo ship or freighter is a merchant ship that carries cargo, goods, and materials from one port to another. Thousands of cargo carriers ply the world's seas and oceans each year, handling the bulk of international trade. Cargo ships are usually specially designed for the task, often being equipped with cranes and other mechanisms to load and unload, and come in all sizes. Today, they are almost always built of welded steel, and with some exceptions generally have a life expectancy of 25 to 30 years before being scrapped.
Bathymetry is the study of underwater depth of ocean floors or lake floors. In other words, bathymetry is the underwater equivalent to hypsometry or topography. The first recorded evidence of water depth measurements are from Ancient Egypt over 3000 years ago. Bathymetric charts are typically produced to support safety of surface or sub-surface navigation, and usually show seafloor relief or terrain as contour lines and selected depths (soundings), and typically also provide surface navigational information. Bathymetric maps may also use a Digital Terrain Model and artificial illumination techniques to illustrate the depths being portrayed. The global bathymetry is sometimes combined with topography data to yield a global relief model. Paleobathymetry is the study of past underwater depths.
Roll-on/roll-off ships are cargo ships designed to carry wheeled cargo, such as cars, trucks, semi-trailer trucks, buses, trailers, and railroad cars, that are driven on and off the ship on their own wheels or using a platform vehicle, such as a self-propelled modular transporter. This is in contrast to lift-on/lift-off (LoLo) vessels, which use a crane to load and unload cargo.
A chart datum is the water level surface serving as origin of depths displayed on a nautical chart. A chart datum is generally derived from some tidal phase. Common chart datums are lowest astronomical tide (LAT) and mean lower low water (MLLW). In non-tidal areas, e.g. the Baltic Sea, mean sea level (MSL) is used.
"Suezmax" is a naval architecture term for the largest ship measurements capable of transiting the Suez Canal in a laden condition, and is almost exclusively used in reference to tankers. The limiting factors are beam, draft, height, and length.
The Panama Canal expansion project, also called the Third Set of Locks Project, doubled the capacity of the Panama Canal by adding a new lane of traffic allowing for a larger number of ships, and increasing the width and depth of the lanes and locks allowing larger ships to pass. The new ships, called New Panamax, are about one and a half times the previous Panamax size and can carry over twice as much cargo. The expanded canal began commercial operation on 26 June 2016.
The draft or draught of a ship's hull is the vertical distance between the waterline and the bottom of the hull (keel). The draught of the vessel is the maximum depth of any part of the vessel, including appendages such as rudders, propellers and drop keels if deployed. Draft determines the minimum depth of water a ship or boat can safely navigate. The related term air draft is the maximum height of any part of the vessel above the water.
In geodesy, surveying, hydrography and navigation, vertical datum or altimetric datum, is a reference surface for vertical positions, such as the elevations of Earth-bound features and altitudes of satellite orbits and in aviation. In planetary science, vertical datums are also known as zero-elevation surface or zero-level reference.
The Rendsburg High Bridge is a railway viaduct on the Neumünster–Flensburg line that also serves as a transporter bridge. The bridge crosses the Kiel Canal at Rendsburg in the German state of Schleswig-Holstein. It is federally owned through the Federal Water and Navigation Administration that also owns and runs the canal.
Shipwrecking is an event that causes a shipwreck, such as a ship striking something that causes the ship to sink; the stranding of a ship on rocks, land or shoal; poor maintenance; or the destruction of a ship either intentionally or by violent weather.
Vertical position or vertical location is a position along a vertical direction above or below a given vertical datum. Vertical distance or vertical separation is the distance between two vertical positions. Many vertical coordinates exist for expressing vertical position: depth, height, altitude, elevation, etc.
Vertical Offshore Reference Frames (VORF) is a set of high resolution surfaces which together define the vertical datum for hydrographic surveying and charting in the United Kingdom and Ireland. The following surfaces are included: