Once you enter, you can go below. However, for a bit of interesting stuff, check out Tetra’s bedroom (the room directly in front of you). I won’t spoil any of it for you. When ready, go to the hold and meet Niko.
Niko seems overjoyed to see you - he thought that you died at the Forsaken Fortress. He decides, as a welcoming gift, to give you your second test. It is somewhat similar to the first, but harder. There are no platforms; you are swinging from one rope to the next.
There is plenty of time (five minutes?) to do this. The main problem is lining up your swing. As you did a few times in the Dragon Roost Cavern, hold R and move the Control Stick left/right to change which direction Link is facing. You want to face towards the next rope, obviously.
Niko is, as always, impressed that you passed the test. He debates for a moment whether to give you something. He eventually does - you got the pirate’s Bombs! Soon after, Tetra contacts you via the charm and is as surprised as Niko that you survived.
She compliments your courage, but derives it by saying that it was only because an idiot like Niko was left to guard the Bombs. Tetra will tell you more about the pearl’s location and that they are leaving at first light tomorrow. Jump from the ledge, climb the ladder, hit the switch and trap Niko for the heck of it, and leave.