The Diamantina Trench is located in the Indian Ocean, hence, option 3 is the correct answer.

Now, let`s dissect other options:

Option 1 - Pacific Ocean: This ocean, although the largest and deepest in the world, is not where the Diamantina Trench is located. It has its own trenches such as the Mariana Trench.

Option 2 - Atlantic Ocean: The Atlantic also has its own deep-sea trenches, however, the Diamantina Trench is not among them. The Puerto Rico Trench, for instance, is in the Atlantic Ocean.

Option 4 - Arctic Ocean: The Arctic Ocean, the smallest and shallowest of the world`s five major oceans, has fewer trenches compared to the others. The Diamantina Trench is not in this ocean.

In conclusion, Diamantina Trench, named after the Australian ship HMAS Diamantina, is within the Indian Ocean according to marine topography.