The warrior stood up, stiff and straight, stretched out his arms, and threw himself into the water. He landed flat on his belly, with a crash that sent the birds screaming out of the trees.

    Ranji dissolved into laughter.
    “Are you trying to empty the pool?” he asked, as the warrior came to the surface, spouting water like a small whale.

    “Wasn’t it good?” asked the boy, evidently proud of his feat.

    “Not very good,” said Ranji. “You should have more practice. See, I will do it again.”

    And pulling himself up on a rock, he executed another perfect dive. The other boy waited for him to come up, but, swimming under water, Ranji circled him and came upon him from behind.

    “How did you do that?” asked the astonished youth.

    “Can’t you swim under water?” asked Ranji.

    “No, but I will try it.”

    The warrior made a tremendous effort to plunge to the bottom of the pool and indeed he thought he had gone right down, though his bottom, like a duck’s, remained above surface.
    Ranji, however, did not discourage him.
   “It was not bad,” he said. “But you need a lot of practice.”
Later, the Warrior did as the Fighter had advised. He then tightened and erectly stood up before spreading his arms and plunging into the water. Unfortunately, the Warrior landed on his belly, causing a crash that scared the birds away, leading them to scream and leave the trees. It indicates that instead of diving, the Warrior leapt into the pool with his belly forward, causing the water to splash out. As a result, the birds screamed out in fear. Ranji burst out laughing after witnessing the Warrior's attempt at diving.
The Warrior swimming on water
The Warrior came to the pool's surface with the splashing of water like a small whale. At the same time, Ranji asked him whether he was trying to drain the pool. It suggests that when he jumped into the pool without knowing how to dive, the water splashed out, and he could not swim properly.
The Warrior, on the other hand, was thrilled with how he completed the dive. He was curious about what Ranji had to say and asked whether he thought it was good. Ranji told him it wasn't good enough and that he needed more practice. It means that Ranji encouraged the boy to succeed. He told the Warrior that he was going to do it again. Later Ranji stood up on the rock and performed another perfect dive.

The Warrior then waited for Ranji to float on the pool's surface. Ranji, on the other hand, instead of reaching him directly, circled him and approached him from behind while swimming underwater. Ranji's act astounded the boy, and he asked him how he did it. Ranji asked the Warrior whether he could not swim underwater. On the other hand, the boy said that he didn't know how to swim underwater but would try anyhow. As a result, the Warrior summoned all of his strength and swam to the pool's bottom.

On the other hand, the Warrior thought he'd made it to the bottom, but his bottom remained just above the surface, like a duck's. It means that the Warrior believed he had reached the pool's bottom but was unaware that he remained on the pool's surface. Ranji then thought that he should not discourage the Warrior. As a result, he told him that it wasn't bad but still required a lot of work.
Meanings of the difficult words:
Stiff Not easily bent or changed in shape; rigid
BellyThe front part of the human trunk below the ribs, containing the stomach and bowels
Screaming Long, loud piercing cries expressing extreme emotion or pain
LaughterThe action or sound of laughing
Spouting Send out liquid forcibly in a stream
National Council of Educational Research and Training (2008). It so happened. The Fight- Ruskin Bond (pp. 45-54). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.