What Is the Difference Between Sharp and Shark?

The word shark can refer to a person who is good at playing cards without cheating, or person who cheats at cards. However, the word sharker alone refers to some one who cheats or is dishonest. A loan shark is known for generally operating outside the laws that regulate money lending to take advantage of people and make a profit. People don't win by cheating, but by skilfully playing the game. In that context, being a shark is a good thing. But consider what happens if we replace the word card with loan.