Sword of Mana/Road to Wendel

After you have gone out of Marsh Cave you should get Undine to the water, to get there, go South, East, South and North-East, if you want to know some more about the mirror then go and See Ms. Isabella, if not then exit Scaly Lair and go down the bridge and go into the cave, switch to Undine and use it on the Seal, then go through.

In the second room of the cave, you will encounter some Iffish, beat them all then go south to Exit the cave, you're almost at Wendel.

Wendel Coast
Here, you will find Pincher Crabs, go south, South east and North to get to Wendel