Johnny is a quite formidable blue fishy-type shark thing, as far as blue fishy-type shark things go. There are a couple of things you might want to have--if you had enough Frog Coins for an Exp. Booster, it's an invaluable item. Mario needs it while you explore the ship, and after you've defeated Johnny give it to Toadstool or Mallow. Secondly, if you managed to find one in the Forest Maze or if you've been REALLY busy at Yo'ster Isle, a Red Essence is a great thingie to have. Mario, Geno, and Bowser are a winning combination. There are two major approaches to fighting Johnny; if you want to avoid having to go against Johnny one-on-one, just ignore the Bandana Blues and go after Johnny from the very start.  However,  I favour is making sure all the Bandana Blues are out of the picture before starting in on Johnny at all; if Mario's strong enough, it won't be a problem, and all those Skewers start to get annoying after a while.  If you don't want to take Johnny on alone, the best thing to do is to kill all of the Bandana Blues *except one*.  If you're determined to make a go of it, replace Geno in your party with Toadstool and keep the Bandana Blue out of the picture with Sleepy Time.  As always, you can do as you like. Don't sweat it when Johnny Gets Tough--you'll be okay. Trust me. Heh heh heh. When Johnny goes toe-to-toe against Mario, don't be afraid to use your turns for mushrooms or syrup! They're essential to your survival! Plus, if you did have a Red Essence, NOW IS THE TIME TO USE IT. Mario's weapon of choice is the Masher, which you can pick up at Booster Tower. If you destroyed Box Boy and explored the flooded section of the ship, you may have picked up the Safety Ring and the Safety Badge. Mario needs the Ring, and Bowser gets the Badge. Geno should have the Amulet, and his weapon should be either the Finger Shot or the Hand Gun. Bowser should have the Hurly Gloves, but if you were seriously short on funds, I suppose the Chomp will do. Just don't freak out, and you'll get Johnny! Make sure you use the trampoline in the next room to get back to the surface, unless you want to equip Toadstool or Mallow with the Exp. Booster and fight your way back up.