相傳很久很久以前，黃河里有一位河神，人們叫他河伯。何伯站在黃河岸上。望著滾滾的浪濤由西而來，又奔騰跳躍向東流去，興奮地說；“黃河真大呀，世上沒有哪條河能和它相比。我就是最大的水神啊！”
有人告訴他：“你的話不對，在黃河的東面有個地方叫北海，那才真叫大呢。”
河伯說：“我不信，北海再大，能大得過黃河嗎？”
那人說：“別說一條黃河，就是幾條黃河的水流進北海，也裝不滿它。”
河伯固執地說：“我沒見過北海，我不信。”
那人無可奈何，告訴他：“有機會你去看看北海，就明白我的話了。”
秋天到了，連日的暴雨使大大小小的河流都注入黃河，黃河的河面更加寬闊了，隔河望去，對岸的牛馬都分不清。這一下，河伯更得意了，以為天下最壯觀的景色都在自己這里，他在自得之余，想起了有人跟他提起的北海，于是決定去那里看看。
河伯順流來到黃河的入海口，，突然眼前一亮，海神北海若正笑容滿面地歡迎他的到來，河伯放眼望去，只見北海汪洋一片，無邊無涯，他呆呆地看了一會兒，深有感觸地對北海若說：“俗話說，只懂得一些道理就以為誰都比不上自己，這話說的就是我呀。今天要不是我親眼見到這浩瀚無邊的北海，我還會以為黃河是天下無比的呢！那樣，豈不被有見識的人永遠笑主。”
故事見于《莊子·秋水》。成語“望洋興嘆”，比喻要做某事而力量不夠，感到無可奈何。
lamenting one's littleness before the vast oceantradition has it that many,many years ago,there lived on the yellow river a river god known as he bo.one day ,he bo stood on the riverbank and watched the turbulent waves from the west surging forward to the east.he said both excitedly and conceitedly:"how big the yellow river is !no other river on earth can compare with it.and therefore i am the greatest river god."
one man said to him,"you are wrong.there is a place to the east of the yellow rivers called the north sea.the north sea is really big."he bo said,"i don't believe it .big as the north sea is, can it be bigger than yellow river?"the man said,"should the water of several yellow river flow into the north sea,it could not fill the north sea,let alone one yellow river. "
he bo said obstinately,"i don't believe it,for i have never been to the north sea."
having no alternative,the man said,"you will not be able to" understand what i mean until you have a chance to see the north sea for yourself."
winter came,and torrential rain had been falling for days on end.rivers big and small emptied themselves into the yellow river,making the yellow river even broader.standing on one side of the river,people could hardly tell what animals the oxen and horses on the other side of the river were.thus he bo was even more proud,thinking that all the magnificent sights were accumulated here.then ,remembering the north sea which had been mentioned to him before,he decided to go there and have a look.
he went downstream,and arrived at the river mouth to the sea.suddenly,the god of the north sea,whose name was biennia ruo,appeared before his eyes.with a smile,beihai ruo was welcoming he bo to the north sea.he looked ahead,and saw that the north sea,with its vast expanse of water,was boundless.with a dull look in his eyes,he bo stood there for a while.finally he said to beihai ruo with deep feeling,"as the common saying goes,some people go so far as to think that they are more knowledgeable than anybody else when they have got some knowledge.actually i am one of such people.if i had not seen with that the yellow river is matchless in the world.if i remained like that, i would be laughed at for ever by sensible people."