In Shemot 7:14-15, Moshe is told to go to the Nile, for Pharoah is there.
וַיֹּאמֶר יְהוָה אֶל-מֹשֶׁה, כָּבֵד לֵב פַּרְעֹה; מֵאֵן, לְשַׁלַּח הָעָם.
לֵךְ אֶל-פַּרְעֹה בַּבֹּקֶר, הִנֵּה יֹצֵא הַמַּיְמָה, וְנִצַּבְתָּ לִקְרָאתוֹ, עַל-שְׂפַת הַיְאֹר; וְהַמַּטֶּה אֲשֶׁר-נֶהְפַּךְ לְנָחָשׁ, תִּקַּח בְּיָדֶךָ.
"And the LORD said unto Moses: 'Pharaoh's heart is stubborn, he refuseth to let the people go.
Get thee unto Pharaoh in the morning; lo, he goeth out unto the water; and thou shalt stand by the river's brink to meet him; and the rod which was turned to a serpent shalt thou take in thy hand."
Rashi cited Shemot Rabba that the reason Pharoah went to the water was to go to the bathroom. Pharoah claimed to be a god, who did not need to go to the bathroom, and he would awake early to go to the Nile and there he would go to the bathroom.
I saw the derivation in Tg Yonatan. In a later pasuk, 7:23, at the end of the encounter:
וַיִּפֶן פַּרְעֹה, וַיָּבֹא אֶל-בֵּיתוֹ; וְלֹא-שָׁת לִבּוֹ, גַּם-לָזֹאת.
"And Pharaoh turned and went into his house, neither did he lay even this to heart."
Tg Yonatan translates וַיִּפֶן פַּרְעֹה as "Pharoah took care of his needs," that is he went to the bathroom. He does not connect this to an attempt to appear as a deity. However, one could possibly make the derivation that he took care of his needs here and only then returned to his house, implying that he did not take care of his needs in his house.
Even so, Tg Yonatan gives a different reason for Pharoah going to the Nile by the first pasuk I cited. He claims it was to do ksamim (magics) upon it. This is actually somewhat supported by the narrative. for after Moshe and Aharon turn the Nile into blood, the magicians do likewise, at which point Pharoah hardens his heart and does not listen to Moshe and Aharon. What are the magicians doing there? It makes sense if he went with them to do magic on the Nile, but less so if he is trying to quietly relieve himself so that no one will know.