The Frog Suit is an item from SPY Fox in "Dry Cereal".
SPY Fox in "Dry Cereal"
The frog suit appears only in the White Water storyline.
In the White Water storyline, SPY Fox will need this suit in order to swim underwater to William the Kid's secret island fortress. He will find the suit in the S.S. Deadweight's shift room. After SPY Fox finds where the White Water is, he must put on the frog suit so he can go underwater and find the secret island fortress. SPY Fox will automatically get out of his Frog Suit whenever he enters the secret island fortress or when he returns back to Captain Drydock's ship.
If SPY Fox returns to the docks after using his frog suit, Captain Drydock will allow SPY Fox to leave his frog suit on his boat, so that SPY Fox can use it whenever they go out to sea without the suit being in SPY Fox's suit.