Let us offer our respectful obeisances to all the great devotees and ācāryas (holy teachers), who are compared with sharks in the great ocean of nectar and who do not care for the various rivers of liberation. Impersonalists are very fond of merging into the supreme, like rivers that come down and merge into the ocean. The ocean can be compared with liberation and the rivers with all the different paths of liberation. The impersonalists are dwelling in the river water, which eventually comes to mix with the ocean. They have no information, however, that within the ocean, as within the river, there are innumerable aquatic living entities. The sharks who dwell in the ocean do not care for the rivers which are gliding down into it. The devotees eternally live in the ocean of devotional service, and they do not care for the rivers. In other words, those who are pure devotees always remain in the ocean of transcendental loving service to the Lord and have no business with the other processes, which are compared to the rivers that only gradually come to the ocean.
Śrīla Rūpa Gosvāmī prays to his spiritual master, Śrīla Sanātana Gosvāmī, for the protection of Bhakti-rasāmṛta-sindhu—the Ocean of the Pure Nectar of Devotional Service—from the argumentative logicians who unnecessarily meddle in the science of service to the Lord. He compares their arguments and logic to volcanic eruptions in the midst of the ocean. In the midst of the ocean such volcanic eruptions can do very little harm, and similarly, those who are against devotional service to the Lord and who put forward many philosophical theses about the ultimate transcendental realization cannot disturb this great ocean of devotional service.
The author of Bhakti-rasāmṛta-sindhu, Śrīla Rūpa Gosvāmī, very humbly submits that he is just trying to spread Kṛṣṇa consciousness all over the world, although he humbly thinks himself unfit for this work. That should be the attitude of all preachers of the Kṛṣṇa consciousness movement, following in the footsteps of Śrīla Rūpa Gosvāmī. We should never think of ourselves as great preachers, but should always consider that we are simply instrumental to the previous ācāryas, and simply by following in their footsteps we may be able to do something for the benefit of suffering humanity.
Bhakti-rasāmṛta-sindhu is divided into four parts, just as the ocean is sometimes divided into four parts, and there are different sections within each of these four divisions. Originally in Bhakti-rasāmṛta-sindhu, the ocean is divided like the watery ocean into east, west, north and south, while the sub-sections within these different divisions are called waves. As in the ocean there are always different waves, either on the eastern side, the western side, the northern side or the southern side, so similarly Bhakti-rasāmṛta-sindhu has different waves. In the first part there are four waves, the first being a general description of devotional service. The second concerns the regulative principles for executing devotional service, and the third wave devotional service in ecstasy. In the fourth is the ultimate goal, love of God. These will be explicitly described along with their different symptoms.
The authorized description of bhakti, or devotional service, following in the footsteps of previous ācāryas, can be summarized in the following statement by Śrīla Rūpa Gosvāmī: "First-class devotional service is known by one's tendency to be fully engaged in Kṛṣṇa consciousness, serving the Lord favorably." The purport is that one may also be in Kṛṣṇa consciousness unfavorably, but that cannot be counted as pure devotional service. Pure devotional service should be free from the desire for any material benefit or for sense gratification, as these desires are cultivated through fruitive activities and philosophical speculation. Generally, people are engaged in different activities to get some material profit, while most philosophers are engaged in proposing transcendental realization through volumes of word jugglery and speculation. Pure devotional service must always be free from such fruitive activities and philosophical speculations. One has to learn Kṛṣṇa consciousness or pure devotional service from the authorities by spontaneous loving service.