--- title: Ships, ports and submarines — a lesson of Mova's school · trees and pragmatics description: «Ships, ports and submarines», a lesson of the technology course of Mova's primary school, sentence by sentence with dependency trees and pragmatics. It begins: The secret is shape: the hollow hull pushes aside a huge amount of water, and the water pushes back up with a force as big as the weight of --- [Mova](https://md.mova.elamur.ai/free/en/) · [this page in HTML](https://mova.elamur.ai/free/en/corpora/school/technology/24-ships-ports-and-submarines/) [home](https://md.mova.elamur.ai/free/en/) / [corpora](https://md.mova.elamur.ai/free/en/corpora/) / [school](https://md.mova.elamur.ai/free/en/corpora/school/) / [Technology](https://md.mova.elamur.ai/free/en/corpora/school/technology/) / Ships, ports and submarines # Ships, ports and submarines Lesson 24 of the technology course of Mova's primary school: 18 sentences, each with its syntax tree and pragmatics. The lessons are written for Mova, and their agreed trees are part of Mova corpus 0.4 (CC BY-SA 4.0). How Mova does on its tests: [the lesson at school](https://md.mova.elamur.ai/free/en/school-run/technology/24-ships-ports-and-submarines/). - [1](https://md.mova.elamur.ai/free/en/corpora/school/technology/24-ships-ports-and-submarines/1/) — The secret is shape: the hollow hull pushes aside a huge amount of water, and the water pushes back up with a force as big as the weight of the water pushed away. - [2](https://md.mova.elamur.ai/free/en/corpora/school/technology/24-ships-ports-and-submarines/2/) — If the ship pushes aside water that weighs as much as the whole ship before its deck reaches the waterline, it floats. - [3](https://md.mova.elamur.ai/free/en/corpora/school/technology/24-ships-ports-and-submarines/3/) — A squashed lump of the same steel pushes aside very little water, so it sinks. - [4](https://md.mova.elamur.ai/free/en/corpora/school/technology/24-ships-ports-and-submarines/4/) — Squash a ball of modelling clay and it sinks in a bowl of water; press the same clay into a little boat and it floats. - [6](https://md.mova.elamur.ai/free/en/corpora/school/technology/24-ships-ports-and-submarines/6/) — Around the ships there is a whole world of machines: cranes stacking containers, lighthouses flashing their own patterns, locks lifting boats up hills of water, and submarines that sink and rise on purpose. - [7](https://md.mova.elamur.ai/free/en/corpora/school/technology/24-ships-ports-and-submarines/7/) — A ship floats because its hollow shape pushes aside water weighing as much as the ship; a steel nail sinks but a steel ship floats. - [8](https://md.mova.elamur.ai/free/en/corpora/school/technology/24-ships-ports-and-submarines/8/) — Never play near harbour edges, quays or mooring ropes; the water is deep and cold and ropes can snap tight. - [9](https://md.mova.elamur.ai/free/en/corpora/school/technology/24-ships-ports-and-submarines/9/) — Container ships carry thousands of metal boxes of standard sizes, so any crane, ship, train or lorry can lift and carry them; most things in our shops travelled part of the way in a container. - [10](https://md.mova.elamur.ai/free/en/corpora/school/technology/24-ships-ports-and-submarines/10/) — Cars drive onto a ferry's big decks, often through doors in the bow that lift up like a mouth; passengers keep to the passenger decks and listen to safety announcements. - [11](https://md.mova.elamur.ai/free/en/corpora/school/technology/24-ships-ports-and-submarines/11/) — A submarine fills its tanks with water to sink and blows the water out with air to rise; its strong walls resist the squeeze of deep water, and some submarines stay under for months. - [12](https://md.mova.elamur.ai/free/en/corpora/school/technology/24-ships-ports-and-submarines/12/) — Big nuclear submarines make their own oxygen from seawater using electricity. - [13](https://md.mova.elamur.ai/free/en/corpora/school/technology/24-ships-ports-and-submarines/13/) — A lifejacket's foam or gas-filled bag keeps your head above water; wear one on boats, and if you fall into cold water, float on your back, keep calm and wave or shout for help. - [15](https://md.mova.elamur.ai/free/en/corpora/school/technology/24-ships-ports-and-submarines/15/) — Each lighthouse flashes its own pattern, so sailors know which one they are seeing; British lighthouses now run automatically, without keepers. - [16](https://md.mova.elamur.ai/free/en/corpora/school/technology/24-ships-ports-and-submarines/16/) — An anchor is a heavy shaped hook that digs into the seabed, and the weight of its chain helps hold the ship; a giant ship's anchor can weigh more than ten cars. - [17](https://md.mova.elamur.ai/free/en/corpora/school/technology/24-ships-ports-and-submarines/17/) — A canal lock lifts or lowers boats by filling or emptying a chamber between gates; the Panama Canal's locks lift ships about 26 metres. - [18](https://md.mova.elamur.ai/free/en/corpora/school/technology/24-ships-ports-and-submarines/18/) — Locks are deep, so stay back from the edge. - [19](https://md.mova.elamur.ai/free/en/corpora/school/technology/24-ships-ports-and-submarines/19/) — A propeller's twisted blades push water backwards as they spin, so the ship moves forward; the biggest ship propellers are taller than a house. - [20](https://md.mova.elamur.ai/free/en/corpora/school/technology/24-ships-ports-and-submarines/20/) — Sonar sends sound pulses down and listens for echoes from the seabed or fish; dolphins and bats use echoes in a similar way. - ← previous: [Airports, the black box, helicopters and drones](https://md.mova.elamur.ai/free/en/corpora/school/technology/23-airports-black-box-helicopters-drones/) - next →: [Bicycles and other wheels](https://md.mova.elamur.ai/free/en/corpora/school/technology/25-bicycles-and-other-wheels/) - ↑ back to [Technology](https://md.mova.elamur.ai/free/en/corpora/school/technology/)