Possible Clues:

• Sea-robber
• Marine menace
• Long John Silver, e.g.
• Without his top he's a cross robber at sea
• When the criminal loses his head it makes him cross
• Menace at sea
• Such a tripe becomes a crook
• Porch ___ (package thief)
• Goody-goody to scold a 12
• I run into head buccaneer