Marala Lake is the fifth zone of Vagabond. It's something of a paradise for the denizens of Granti, considering there are very few monsters around and the lake is a great place to hang out. However, to traverse the lake one must have a raft of some sort. There's one guy who can hook you up, though he's a bit strange...
"Right, uh, I'll just be leaving..."
Fario here has a raft (as well as a few great augments!) up for trade, but he's not looking for just any old item. He wants Lucky Medals. These medals don't appear until you talk to Fario for the first time, but once you do you'll be able to find one in each zone except for the last. You only need one for the raft though, which you can use to reach the Crystal Cavern.
"I am NOT going to slip on the ice this time!"
This dungeon is the bulk of the Marala Lake zone, and yes, it has ice sliding puzzles. It's also home to the Furnace Orb item, which allows you heat up certain rooms, melting the ice, allowing progression with the raft or by other means.
Left: Room without Furnace Orb.
Right: Room with Furnace Orb.