waterline

waterline — noun

1. The line on a ship's or boat's side where the surface of the water meets the hul

1.nounB2
Definition

The line on a ship's or boat's side where the surface of the water meets the hull. This line moves up or down depending on how much weight the vessel is carrying.

Example

Nikhil watched the ferry's waterline rise as more passengers stepped on board.

waterline + verb of movement (rise, fall, sit)

Divers inspected the hull below the waterline for cracks after the storm.

below the waterline

Common collocations
  • above the waterline
  • below the waterline
  • at the waterline
  • waterline rises/falls/sits
  • ship's waterline
Synonyms
  • water level

    Broader term usable for rivers, tanks, or any body of water; less specific to ships

  • load line

    Refers specifically to the painted regulatory marking on a ship, not the actual water contact line

  • Plimsoll line

    A type of load line named after Samuel Plimsoll; formal and technical, less common in everyday speech

Grammar Patterns

the waterline + of + noun

above/below the waterline

Usage Note

Often used with prepositions above, below, or at to describe position relative to the water's surface. The phrase 'below the waterline' is also used figuratively to mean hidden from public view.

Common Mistakes

The ship's watermark rose after loading cargo.
The ship's waterline rose after loading cargo.
A watermark is a mark showing a past water level, not the current line where water meets a vessel.
The draft is the line where water meets the hull.
The waterline is the line where water meets the hull; the draft is the vertical depth below that line.
Draft and waterline are related but distinct concepts.

2. The highest point that water from a sea, river, or lake reaches on the shore, ba

2.nounB2
Definition

The highest point that water from a sea, river, or lake reaches on the shore, bank, or land. This level can change with tides, rainfall, or seasonal flooding.

Example

Romi spotted an old waterline high on the cliff from a flood years ago.

old waterline — mark left by past water level

After the typhoon, the waterline along the riverbank had climbed more than two metres.

Common collocations
  • old waterline
  • waterline rises/climbs
  • waterline falls/recedes
  • waterline along the riverbank/coast
  • measured the waterline
Synonyms
  • shoreline

    Describes the boundary where land meets water as a fixed geographical feature, not the variable water level

  • water level

    More general term usable for any body of water; less specific to the land interface

  • high-water mark

    Emphasises the highest point reached, often as a visible stain or debris line

Grammar Patterns

the waterline + of + [sea/river/lake]

waterline + verb + [preposition]

Usage Note

Frequently used with verbs that describe change, such as rise, climb, fall, move, or recede. Geographers and environmental scientists use this term to track coastal erosion and flooding patterns.

Common Mistakes

The shoreline rose after the storm.
The waterline rose after the storm.
Shoreline refers to the fixed boundary line of the land itself, whereas waterline refers to the moving level of water on that land.

3. A pipe that carries water as part of a supply system, usually to buildings or th

3.nounB2
Definition

A pipe that carries water as part of a supply system, usually to buildings or through a city. Damage to a waterline often causes leaks or flooding.

Example

Harper called the plumber after a burst waterline flooded the kitchen floor.

burst waterline

The city replaced the old iron waterline with a wider plastic pipe.

Common collocations
  • burst waterline
  • broken waterline
  • replace a waterline
  • repair a waterline
  • waterline floods
Synonyms
  • water pipe

    More general term for any pipe that carries water; less specific to supply systems

  • water main

    Refers specifically to the main underground pipe in a public supply system, not a branch pipe to a building

  • supply line

    Broader term that can carry water, gas, or other utilities; less specific

Grammar Patterns

a waterline

the waterline + [verb of damage/repair]

burst/broken waterline

Usage Note

Common in construction, plumbing, and municipal infrastructure contexts. In British English, this is often called a water main when it refers to the main supply pipe in a street.

Common Mistakes

A burst waterline spilled oil across the road.
A burst waterline spilled water across the road.
A waterline carries water by definition, not other liquids.

4. A painted mark on a ship's exterior showing the correct depth at which the water

4.nounC1
Definition

A painted mark on a ship's exterior showing the correct depth at which the water should reach the hull under normal loading conditions. It serves as a visual guide for safe loading.

Example

The shipyard workers repainted the waterline on the hull during the annual maintenance.

repainted the waterline

Emre explained that the waterline markings show whether a ship is carrying too much weight.

Common collocations
  • waterline markings
  • repaint the waterline
  • waterline on the hull
  • painted waterline
  • waterline visible
Synonyms
  • load line

    More formal term used in international shipping regulations; often interchangeable with waterline in sense 4

  • Plimsoll line

    A specific type of load line named after Samuel Plimsoll; required by law on most commercial vessels

  • draft mark

    A numerical marking near the waterline that shows the vessel's current draft in metres or feet

Grammar Patterns

the waterline markings

repaint the waterline

waterline on the hull

Usage Note

This is a technical sense used mainly in shipbuilding and maritime safety. It is closely related to the Plimsoll line (load line) but waterline here refers to the painted mark itself, not the regulatory certification. Distinguish from sense 1, which describes the actual physical water level on the hull rather than the painted guide.

Common Mistakes

The ship's waterline sank after loading cargo.
The ship's waterline marking stayed the same, but the actual water level on the hull rose.
The painted waterline does not move; it is a fixed mark.
Idioms

below the waterline

idiom

Used figuratively to describe problems, weaknesses, or damage that are hidden or not obvious to others, like part of a ship that is underwater.

The company's financial troubles stayed below the waterline until the annual report was published.

Noa felt that the team's real problems were below the waterline, invisible to the new manager.

Synonym discussion

Sense: noun/1

Waterline (sense 1) refers to the line where water currently meets a ship's hull. Water level is a much broader term — it can describe the height of water in a glass, a reservoir, or a river — whereas waterline is specifically maritime. Watermark describes a visible mark left on a surface (a wall, a bridge pillar) showing how high water once reached; unlike waterline, it records a past level, not the current one. Shoreline describes the fixed edge of land where it meets a large body of water, focusing on the land boundary rather than the ship. Draft (also spelled draught) measures the vertical depth of a ship below the waterline — it tells you how much of the hull sits underwater. For example: 'The captain checked the waterline after loading' (current water level on hull); 'The flood left a watermark on the wall' (past mark); 'The shoreline had moved inland' (land-water edge); 'The vessel has a draft of nine metres' (underwater depth).

water levelwatermarkshorelinedraft ↗

Common collocations

Nouns

Adverbs

Phrases

Prepositions

Etymology

Old EnglishMiddle EnglishEnglish

Waterline is a compound of the Old English words 'wæter' (water) and 'līne' (a cord, rope, or series). It was first used in the 1400s in shipbuilding, describing the horizontal line on a vessel's hull where the water surface meets the side. In the following centuries the word expanded to describe water levels on shores and riverbanks, and by the 1800s it was also being used for the pipes that carry water through cities and buildings.