Some scholars believe that this people had already heard of the two oceans. This point again is doubtful in the extreme. No descriptions imply a knowledge of ocean, and the word for ocean means merely a 'confluence' of waters, or in general a great oceanic body of water like the air. As the Indus is too wide to be seen across, the name may apply in most cases to this river. An allusion to 'eastern and western floods,'[17] which is held by some to be conclusive evidence for a knowledge of the two seas, is taken by others to apply to the air-oceans. The expression may apply simply to rivers, for it is said that the Vip[=a]ç and Çutudr[=i] empty into the 'ocean', i.e., the Indus or the Çutudr[=i]'s continuation.[18] One late verse alone speaks of the Sarasvat[=i] pouring into the ocean, and this would indicate the Arabian Sea.[19] Whether the Bay of Bengal was known, even by hearsay and in the latest time of this period, remains uncertain. As a body the Aryans of the Rig Veda were certainly not acquainted with either ocean. Some straggling adventurers probably pushed down the Indus, but Zimmer doubtless is correct in asserting that the popular emigration did not extend further south than the junction of the Indus and the Pa[=n]canada (the united five rivers).[20] The extreme south-eastern geographical limit of the Rig Vedic people may be reckoned (not, however, in Oldenberg's opinion, with any great certainty) as being in Northern Beh[=a]r (M[=a]gadha). The great desert, Marusthala, formed an impassable southern obstacle for the first immigrants.[21]