Theory:

Most of us have seen a tortoise in a zoo or a reptile park. However, not many would have seen its marine relative, the sea turtle. This is not surprising, since these reptiles spend almost their entire life in the sea.

There are seven species of marine or sea turtles in the world. Of them, five are found in India’s coastal waters: the Olive Ridley, the Hawksbill, the Green Sea Turtle, the Loggerhead and the Leatherback. Compared to most tortoises, sea turtles are huge. Even the smallest species, the Olive Ridley, weighs up to 35 kg when fully grown. The largest of them all, the Leatherback, grows to a length of 2.2m and each could weigh as much as 700 kg!

Sea turtles live their life entirely in the oceans. But they still have a connection with land – they must come ashore to lay eggs. Today, four of the sea turtle species mentioned above have become extremely rare in India. The Olive Ridleys, however, are still commonly seen nesting on sandy beaches all along our coasts.
Explanation:
  
turtle.jpg
 
We have seen tortoises in a zoo or a park. But, most of us would not have seen a sea turtle.
  
Is the sea turtle different from tortoise? Yes. They are relatives but not the same. Why most of us would not have seen a sea turtle? Because these reptiles (a species of animals that have scaly skin and lay soft-shelled eggs on the land; includes lizards, crocodiles also) live their entire life in the sea.
  
There are seven different types of marine or sea turtles in the world. Out of seven, five are found in our Indian seas. They are:
 
  • the Olive Ridley - the smallest species, most common - 35 kgs when fully grown.
  • the Hawksbill
  • the Green Sea Turtle
  • the Loggerhead
  • the Leatherback - the largest species - 700 kgs and 2.2 metres in length.
Sea turtles are much bigger than most tortoises. They live their life fully in oceans - but they come to land (shore) to lay eggs. Of the above five species, four have become rare species in India. The most common ones are the Olive Ridleys, which can be still seen on all sandy beaches along our coasts.
 
Meanings of difficult words:
 
Words
Meanings
ReptilesScaly animals that lay soft-shelled eggs.
MarineFound in the sea.
SpeciesGroup of animals with common features.
CoastalLand near the edge of the sea, seashore.
Reference:
State Council of Educational Research and Training (2019). Term-1 English Standard-6. Sea Turtles - Shekar Dattatri (pp. 86-92). Published by the Tamil Nadu Textbook and Educational Services Corporation.