Submarines are large, crewed, autonomous vessels that operate underwater. While submarines are usually referred to as boats regardless of size due to naval tradition, the term submarine can also refer to smaller, remotely operated underwater vehicles or robots. Key characteristics of submarines include their ability to operate independently underwater through crewed operation or remote control, as well as being described as "under the sea" when used in terms like submarine cable.

1. Submarines

2. Facts
 It differs from a submersible, which has
more limited underwater capability.
 The term submarine most commonly
refers to a large crewed autonomous
vessel.
 However, historically or colloquially,
submarine can also refer to medium-sized
or smaller vessels (midgetsubmarines,
wet subs), remotely operated vehicles or
robots.

3. Here is a submarine

4. More facts
 The adjective submarine, in terms
such as submarine cable, means
“under the sea”.
 For reasons of naval tradition
submarines are usually referred to
as “boats” rather than as “ships”,
regardless of their size.

5. Pictures inside a submarine

12. How to make a
submarine

13. Step 1
Drill a hole in the bottom of
your bottle.

14. Step 2
Using chopsticks, feed a
paper clip through.

15. Step 3
Hook paper clip into second
hole for stability.

16. Step 4
Use chopsticks to hook the
rubber band to the paper clip.

17. And that is
how to make
your own
submarine