Talmud for Shabbat 217:10

רבי יוסי אומר כל הימים מטהרין בזוחלין ופסולים לזבים ולמצורעים ולקדש בהן מי חטאת מתקיף לה רב נחמן בר יצחק

and in the water of Tiberias,<span class="x" onmousemove="('comment',' Though all these are salty, it is permitted, as it does not look that one is bathing particularly for medicinal purposes (v. p. 527, n. 16). ');">²⁵</span> but not in the Great Sea [the Mediterranean], or in the water of steeping,<span class="x" onmousemove="('comment',' In which flax was steeped. ');">²⁶</span> or in the Lake of Sodom. But this contradicts it: One may bathe in the water of Tiberias and in the Great Sea, but not in the water of steeping or in the Lake of Sodom. Thus [the rulings on] the Great Sea are contradictory. — Said R. Johanan, There is no difficulty: one agrees with R. Meir, the other with R. Judah. For we learnt: All seas are like a mikweh,<span class="x" onmousemove="('comment',' v. Glos. They are like a mikweh in all respects, and not like a spring. The difference between these two are: (i) a zab can have his ritual bath in a spring, but not in a mikweh; (ii) the water of a spring, but not of a mikweh, is fit for sprinkling upon a leper (Lev. XIV, 5) and for mixing with the ashes of the red heifer (Num. XIX, 17); (iii) the water of a spring purifies when running, whereas a mikweh purifies only when its water is still (v. supra 65a bottom and b top and notes a.l.). — Since R. Meir maintains that all seas are alike, he draws no distinction in respect to bathing either, and permits it in the Great Sea too. ');">²⁷</span> for it is said, and the gathering of [mikweh] the waters called he Seas:<span class="x" onmousemove="('comment',' Gen. I, 10. ');">²⁸</span> this is R. Meir's view. R. Judah said: The Great Sea [alone] is like a mikweh, 'seas' being stated only because it contains many kinds of waters.<span class="x" onmousemove="('comment',' Many different rivers flow into the sea, hence the plural; but actually the verse refers to the Great Sea only. Thus he draws a distinction between the Great Sea and other seas, and so he also forbids bathing therein on the Sabbath. ');">²⁹</span> R. Jose maintained: All seas [including the Great Sea] purify when running,<span class="x" onmousemove="('comment',' Since that is the nature of seas. ');">³⁰</span> but they are unfit for zabim, lepers, and to be sanctified as the water of lustration.<span class="x" onmousemove="('comment',' I.e., to be mixed with the ashes of the red heifer. ');">³¹</span> R. Nahman b. Isaac demurred:

Jerusalem Talmud Shabbat