SB 4.22.40
krcchro mahan iha bhavarnavam aplavesam
sad-varga-nakram asukhena titirsanti
tat tvam harer bhagavato bhajaniyam anghrim
krtvodupam vyasanam uttara dustararnam
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The ocean of nescience is very difficult to cross because it is infested with many dangerous sharks. Although those who are nondevotees undergo severe austerities and penances to cross that ocean, we recommend that you simply take shelter of the lotus feet of the Lord, which are like boats for crossing the ocean. Although the ocean is difficult to cross, by taking shelter of His lotus feet you will overcome all dangers.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Material existence is compared herein to the great ocean of nescience. Another name of this ocean is Vaitarani. In that Vaitarani Ocean, which is the Causal Ocean, there are innumerable universes floating like footballs. On the other side of the ocean is the spiritual world of Vaikuntha, which is described in Bhagavad-gita (8.20) as paras tasmat tu bhavo ’nyah. Thus there is an ever-existing spiritual nature which is beyond this material nature. Even though all the material universes are annihilated again and again in the Causal Ocean, the Vaikuntha planets, which are spiritual, exist eternally and are not subject to dissolution. The human form of life gives the living entity a chance to cross the ocean of nescience, which is this material universe, and enter into the spiritual sky. Although there are many methods or boats by which one can cross the ocean, the Kumaras recommend that the King take shelter of the lotus feet of the Lord, just as one would take shelter of a good boat. Nondevotees, who do not take shelter of the Lord’s lotus feet, try to cross the ocean of nescience by other methods (karma, jñana and yoga), but they have a great deal of trouble. Indeed, sometimes they become so busy simply enjoying their troubles that they never cross the ocean. There is no guarantee that the nondevotees will cross the ocean, but even though they manage to cross, they have to undergo severe austerities and penances. On the other hand, anyone who takes to the process of devotional service and has faith that the lotus feet of the Lord are safe boats to cross that ocean is certain to cross very easily and comfortably.
Prthu Maharaja is therefore advised to take the boat of the lotus feet of the Lord to easily cross over all dangers. Dangerous elements in the universe are compared to sharks in the ocean. Even though one may be a very expert swimmer, he cannot possibly survive if he is attacked by sharks. One often sees that many so-called svamis and yogis sometimes advertise themselves as competent to cross the ocean of nescience and to help others cross, but in actuality they are found to be simply victims of their own senses. Instead of helping their followers to cross the ocean of nescience, such svamis and yogis fall prey to maya, represented by the fair sex, woman, and are thus devoured by the sharks in that ocean.