Can I ask how this photo was obtained. From my understanding, this can't be seen from the naked eye due to interstellar dust and such?

Few hours for her, months for them. Same with Mathew and the dude on the ship. It's weird but perspective is what it's all about. Remember, both people are experiencing time as normal, but relative to each other, one is slower and one is faster

The way I understand it (no way am I a great source) but it's all about perspective. For those on the water planet, time moved normally, but because they were closer to the gravitational center of the black hole, their "normal" was much slower than the ships. (Why? Not sure that we know exactly. The reason is the massive gravitational pull warping time and space itself).

So, for those on the water planet, if they were looking through a telescope, the guy on the ship would be moving at super speed.

For the guy in the ship looking down, the people/giant wave would be moving in super slow motion.

The part where it talks about the lady to first arrive on the water planet who is now dead, explains this better. She is on the planet, gets hit by a wave and dies. Her signal thing sends out a frequency which is picked up by Mathew and his crew. They go all the way across space to get to the water planet.

Think of timeline here. They probably first got the signal once the first lady arrived. And in that time, they traveled across space, just to have missed her dying by a slim fraction. Meaning, while she was dying, they were moving SUPER fast to reach the planet.

I'm hoping this helps a little. It's hard to grasp the full "why" because we don't know much about space/time continuum and how warping reality is done.