Hi! Few not very important, but annoying things I can't solve... 1...

1. Yes you can catch a Hylian Loach, it's difficult as there are not many in the area. Try using the sinking lure/bee bait.

2.No idea, sorry.

1. The Hylian Loach, as referred to above, can be found in two locations. A small, baby one can be caught past the hole in the wall in the Kakariko Graveyard, near Zora's Tomb. A larger one is in the fishing hole's Northern cove in the Summer. (The seasons will change every time you enter and exit the fishing hole.) Use the Frog or Sinking Lure to catch one.

2. I can't find a chest on a platform in the middle of a small pond. All I can find is a shallow area of water with a bridge over it, but there's no platform. Even if I had got the chest, there would still be a platform. Sorry.

For part 2 of your question if the chest is under water put on the iron boots and zora armour and walk up to it and open it like a normal chest above water

1. The fish she talks about is the loach. It can only be caught with the frog lure or the sinking lure.

2. To get to the chest, there is a clawshot target on a pillar behind the fountain. Grab onto the target and drop down. You will see spinner tracks to the right. Use the spinner and jump. If you timed it right,you should be on the platform.

I know which chest you speak of. Despite beating the game 3 times, I had not found a solution. I started a fourth game and saw the solution. When you first enter the area, coming from the castle town, there are 2 pillars, one of which has a place you can latch onto with your clawshot. Do so, and then drop down. There is a bar connecting the 2 pillars, which I believe you can use the spinner on. I would guess that jumping from the middle of the bar will land you on the platform. Haven't tried it, but plan to do so soon. Hope that helps.