Siman 228

We learned in a Mishnah at the beginning of the chapter "HaRo'eh" (Berakhot 54a): "Upon mountains, and upon hills, and upon seas, and upon rivers, and upon deserts, one says: 'Blessed is the Author of the work of creation.' Rabbi Yehuda says: One who sees the Great Sea says: 'Blessed is He Who made the Great Sea.'" And the matter is simple that we require mountains and hills that are exceptional in their height, such as the Alps, and the Pyrenees, and Mount Kazbek, and the Mountains of Ararat and the like, and rivers as well must be large such that they have a name in the world, and not small rivers that do not have a name in the world.

And behold, the words of the Rambam and the Tur are opaque like the language of the Mishnah, but the wording of our teacher, the Beit Yosef, is as follows: "One does not recite the blessing over all rivers, but rather over the four rivers written in the verse, such as the Tigris and the Euphrates, and this is provided that he saw them in the place of their flow where they have not been changed by man. And one does not recite the blessing over all mountains and hills, but specifically over mountains and hills that are exceptional and the power of the Creator is recognizable in them." Thus far his words. And behold, that which he wrote: 'only over the four rivers in the Torah' is a wondrous thing, and they have already raised this difficulty against him (see Magen Avraham). And in the Mordechai it is written: "such as the four rivers," meaning rivers that have a reputation similar to the four rivers in the Torah. Furthermore, his wording is not understood; what is this that he says: 'such as the Tigris and the Euphrates,' as if we do not know the rivers in the Torah? Therefore, it seems in my humble opinion that it must be said as follows: 'but rather similar to the four rivers written in the verse.' And that which he says: 'such as the Tigris and the Euphrates' is because they are known, whereas the Gihon and Pishon are not known to us. According to this, certainly over the great rivers such as the Volga, Danube, Rhine, and the like—one must recite the blessing. (And that which he ruled according to Rabbi Yehuda, so wrote the Rambam. And the Tur wondered about him, see there, and it is not difficult at all, for he holds that Rabbi Yehuda does not disagree; see Beit Yosef and Bach).

And what is the Great Sea? Our teacher, the Beit Yosef, wrote that it is the sea through which one passes to Eretz Yisrael and to Egypt, and this is the sea in the middle of the inhabited world, one end of which is near Jaffa, which is the border of Eretz Yisrael, and the other end is at the edge of the land of Spain. And there are those who wrote that it is the Ocean that surrounds the entire world (Magen Avraham in the name of Lechem Chamudot), and ostensibly this is the primary view. For granted that the Torah called the sea adjacent to Eretz Yisrael "the Great Sea," this is because among the seas surrounding Eretz Yisrael, it is the largest of them; but in the language of the Mishnah regarding the blessing, why would it be appropriate to call it "the Great Sea," for is it not as nothing and naught compared to the Ocean? Furthermore, in Mikvaot (Chapter 5, Mishnah 4), Rabbi Yehuda also says: "the Great Sea is like a mikvah," and there they explained that this refers to the Ocean; see there.

In my humble opinion, the primary view appears to be like the words of our teacher, the Beit Yosef, for when we examine the works of creation, where the Holy One, Blessed be He, said: "Let the waters be gathered to one place and let the dry land appear," and the waters are the waters of the ocean that surround the earth, and afterwards it is written: "And God called the dry land Earth, and the gathering of the waters He called Seas." And it appears to me that this is the explanation: "And the gathering of the waters," which are in the midst of the dry land, meaning all our seas which are within the globe of the earth, "He called Seas." It follows that according to this, the ocean is called "Water," as it is the element of water, and "Seas" are called those that are within the terrestrial globe. And within the terrestrial globe, the sea that is next to Eretz Yisrael is the largest of all the seas within the globe, as is known from the map of the earth, and also in Mikvaot it is explained thus. (For Rabbi Meir says: "All seas are like a mikvah," meaning all the seas within the globe. And Rabbi Yehuda says: "The Great Sea is like a mikvah," meaning the sea next to Eretz Yisrael into which many seas and rivers flow, as is known. But the commentators did not explain it thus, and according to this, in practice, it appears one should recite over all of them "Who makes the work of creation," even over the sea next to Eretz Yisrael, and also over the ocean, due to the variation in explanations; and delve into this.)