Please explain what this couplet means to you.

Please explain what the first couplet means to you. Thanks!
न जाने  डूबने वाले ने  क्या कहा  समंदर से 
कि लहरें आज तक साहिल पे अपना सर पटकती हैं  

Na Jaane doobnay waalay ne kya kahaa samander say
Ke Lehren aaj tak saahil pay apnaa sar patakati hain

                                                         (Writer: Unknown)
~~~~~~~~~~~~~~

Poetry, as we all know, is very different than prose – especially the sher and Ghazal style – where the poet has to convey the whole message just in two lines. Another interesting feature of Indian and Persian poetry is its metaphoric style. Quite often, the Shaayer or poet chooses to convey the message in an indirect way or by choosing intricate multi-meaning words, so that it could be translated in few different ways. Therefore, sometimes it is very difficult to understand what exact thought the poet had when he or she wrote it. But that is the beauty of this kind of poetry that the listeners or readers can translate it in their own way and relate it to themselves - to their own experience. 

It’s really hard to know what the writer of this sher had in his mind when he wrote it. 
However, in the field of spirituality, it could be taken as:
"Who knows what exactly the people who drowned themselves into the ocean of knowledge – in the realm of spirituality said 
And those, who are floating on the surface like the waves – keep struggling to understand the true meaning – by going back and forth". 
As Kabeer ji said:
जिन खोजा तीन पाया गहरे पानी पैठ 
मैं बौरी ढूँढ़न गई रही किनारे बैठ 
“Jin khoja tin paayeaa geharay paani paaith
Main bauri dhoondan gayee, rahee kinaare baith”

“Those who went deep into the ocean, found the treasures.
  I also went in search but stayed only at the banks” 

There is no way to find out or feel exactly what Kabeer ji had experienced himself by going deep into the ocean of Gyana, Prem and Bhakti. Scholars, till today, keep on trying to explain his experiences in so many different ways. There are so many different commentaries written on his works – many have written thesis for their Ph.D. on his poetry and yet it’s like hitting their heads on the shore. Because it is extremely hard to feel what Kabeer ji felt – just by reading his couplets and sayings. 

This is one way to understand it but as I said, many other meanings can be derived by individuals according to their own interest and understanding. 
                                ‘Rajan Sachdeva’