The first creation is water. The Prophet, sallallahu ^alayhi wa sallam, said:
إِنَّ اللهَ تَعَالَى خَلَقَ كُلَّ شَيْءٍ مِنَ الْمَاءِ
Innallaha ta^ala khalaqa kulla shay’im minal-ma’.
Which means: “Allah created everything from water.” (Related by Ibn Hibban.)
This also means that Allah created water before creating light, darkness, Earth, the heavens, the Throne, or the Guarded Tablet. Allah made water the origin for other creations. He created the Throne from water. Then He created the Upper Pen, then the Guarded Tablet. After these creations, Allah created the rest of the creations: the Earth, heavens, animals, mountains, trees, and rivers. Adam, peace be upon him, was of the last kind of creation, humans.