Henry Trengrouse was a man who lived a long time ago, during the 1700s and 1800s. He was born in Cornwall, which is a place in England. He was a smart man and he liked to invent things that would help people.
One of the things that Henry Trengrouse invented was a device to help people who were in danger in the water. This device was called a "rocket life-saving apparatus". It looked like a big tube with a rocket on top. When someone was in trouble in the water, the rocket would shoot up into the sky and a rope would come out of it. The rope would be attached to a little boat, which would then go out to the person who needed help. The person could hold onto the rope and be pulled to safety.
Henry Trengrouse's invention helped save many people who were in danger in the water. The rocket life-saving apparatus was used by the coastguard and other people who worked near the sea. It was a very important invention because it made it easier to rescue people who might have drowned otherwise.
Even today, we use similar devices to rescue people who are in trouble in the water. Henry Trengrouse's invention was very clever and it helped lots of people.