Ok I'm in Coastal Remains & I'm at the beach where on one side you go to..

Since it's been a few days since this was asked you may have figured it out by now but I'll answer anyway.

From the teleporter when you first get there go toward the shop guy and go to his left there's a pathway tucked into the corner, it looks like a shell. From here take the immediate right, there's a path behind the armored axe-gnorc on top of the ledge, use electric breath to stun him when you're jumping up there so he doesn't hit you while you're trying to get up. Now the path behind him has swinging shell traps, not too hard to get past these ones they have a wide swing, using charge will help. This is where it gets interesting, first jump across to where the dark crystal and axe-grorc is, there's a air lift next to the legde where you first enter if you fall. Kill him smash the crystal and then some platforms will raise up from under water. Facing the platform with the cannon there will be an air lift on the right you can jump and glide to it from the platform that had the dark crystal, from the air lift jump and glide to the cannon platform and shoot the star on the wall, the cannon has a full 360 rotation so you can shoot the strong chests on all the platforms and get a nice chunk of gems, you'll need to use the spin poles to get to some of them. It's tricky but worth it, there's also a dragon egg on the last platform with 2 strong chests. Remember that hole you blasted in the wall? Jump and glide back to the air lift and then jump and glide from the air lift to the hole, you'll need to turn around mid-glide, CAREFUL THOUGH there's more swinging shell traps here and one is near the entrance so don't glide in to far, these ones have a shorter swing and are trickier to get past, again charge will help, even more so with these ones. Once you get past those you'll be standing at the dark crystal on the ledge you were talking about, smash it and some ledges will form on the right that will give you free access back up to it. The dragon egg you get by gliding down to the ruined walls below and jumping across floating shell platforms, they move. The Light Crystal I don't know how to get yet because I'm answering this as I'm playing this for the first time. I'm guessing there'll be a platform that lifts up or an ability maybe that lets you get to it.