Перевести предложения в present perfect tense )дети плавают уже полчаса )они работают в саду с 8 часов )наконец я нашел книгу , которую искал целый день.

The children have already been swimming for half an hour.
They have been working in the garden from 8 o'clock.
At last I have found a book which I have been looking for the whole day.