Bhashya
सर्वास्वप्सु पञ्चविध साम उपासीत ।वृष्टिपूर्वकत्वात्सर्वासामपामानन्तर्यम् ।मेघो यत्सप्लवते एकीभावेनेतरतरघनीभवति मेघ यदा उन्नत, तदा सप्लवते इत्युच्यते,तदा अपामारम्भ स हिंकार, यद्वर्षति स प्रस्ताव, आ-प सर्वतो व्याप्नु प्रस्तुता ।या प्राच्य स्यन्दन्ते स उद्गीथ, श्रेष्ठ्यात्, या प्रतीच्य स प्रतिहार, प्रतिशब्दसामा-न्यात्, समुद्रो निधनम्, तन्निधनत्वादपाम् ॥
In plain words
One should meditate upon the fivefold sāman in all waters, for all waters follow an unbroken sequence originating in rain. When clouds coalesce and condense together, rising high in the sky, that gathering is the beginning of water and serves as the hiṃkāra. When it rains, bringing forth waters that spread on every side, that is the prastāva. The streams that flow eastward are the udgītha, due to their preeminence. Those that flow westward are the pratihāra, owing to the likeness of an echo. And the ocean is the concluding nidhanam, because all waters find their final rest within it.
Close to the Sanskrit
In all waters one should meditate upon the fivefold sāman. Because of being preceded by rain, there is continuity of all waters. When the cloud floats together, condensing mutually, when the cloud is high, then it is said to float together; then the beginning of water is the hiṃkāra. When it rains, that is the prastāva, waters having been brought forth pervading everywhere. Which [rivers] flow eastward, that is the udgītha, because of preeminence. Which flow westward, that is the pratihāra, because of the similarity of counter-sound. The ocean is the nidhanam, because of waters terminating in it.