The word 'Swim' can be found in the aquarium in the green plant behind the castle.
Finding the Word 'Tank'
The word 'Tank' can be found on the side of the scuba divers air tank.
Skate in the Aquarium
This can be found between 2 shells and does not look like a skate. It is in the front toward the left when you are facing the wall. In front of a column at the bottom.