We saw porpoises swimming near the boat.

我们看到海豚在船附近游泳。

Fishermen often spot porpoises while out at sea.

渔民们在海上经常看到海豚。

Porpoises are known for their playful behavior.

海豚以其爱玩耍的行为而闻名。

The aquarium has a special exhibit featuring porpoises.

水族馆有一个特别展览，展示海豚。

The marine biologist studies porpoises in their natural habitat.

海洋生物学家在自然栖息地研究海豚。

Porpoises and sharks are natural enemies.

海豚和鲨鱼是一对天敌.

In 1928 some porpoises were photographed.

1928年，有人拍摄到了海豚。

What would you say is the main characteristic of porpoises?

你认为海豚的主要特征是什么?。

I wondered that the porpoises had long since gone away.

我感到十分惊奇，那些海豚早就离开了。

I wondered that the porpoises had not long since gone away.

我感到十分惊奇， 那些海豚不久前才离开。