It appears that the space sharks have very few weaknesses, one of which is that they cannot withstand the pull of a Black Hole. Aside from that, the space sharks are also rather slow as compared to your spaceship and will give up chasing you if you fly too far ahead.
The three space sharks guard Ice Planet, and you cannot land there until the area is rid of them. According to the spaceship databank, the sharks are practically indestructable, so your lasers will not defeat them.You must lure them into the Black Hole in order to destroy them.
Bag of Manure | Coil of Rope | Coordiantes | Cosmic Symbols | Force Shield | Fuel Rod | Golden Coin | Ice Arrow | Island Medallion | Laser Lance | Library Book Slip | The Life of Mordred: A Cautionary Tale | Mechanical Mouse | Missing Page from Mordred's Journal | Moldy Cheese | Mordred's Journal | The Mystical Weapons of Arturus | Museum Pamphlet | Princess' Note | Secret Message | Small Key