Were humans originally on the planet called Tiamat, where you said the current Earth’s water originated?

This is not the case. The divine human has been present on Earth and its various locations but never on Tiamat or other planets within the solar system, at least as a product of divine implementation of the incarnation intended to create a colony of beings. Humans have indeed traveled throughout the solar system in collaboration with the physical extraterrestrial intruders, but that is a different matter.