>> Swim across moat, blend in as a fish.

Are you crazy?! There are PIRANHA in the MOAT!

>> If above does not work, chop down a tree to fall over the moat, creating a makeshift bridge to cross.

PIR. AN. HA. NO YOU ARE NOT CROSSING THE MOAT.

>> Climb a damn tree and see if you can see into that window.

You run over and climb a nearby TREE in an attempt to peak into the CASTLE's high WINDOW.