SEGA Genesis Classics

Once you've loaded up the game, make sure you choose 'One Player - Toejam or Earl' and 'Play New Game - Fixed or Random'. Now once you're in the game, you're going to just go through the game picking up every present you see. Once you've grabbed one, press (B) to open your menu then (A) to open your presents. What you're looking for are certain objects that can help you get to the secret island. So be on the look out for items like; Rubber Duck Inner-tube, Rocket Boots or Icarus Wings.

Once you've found what you're looking for, simply keep falling off the edge of the worlds you're on until you finally land back on level 1. With the item equip, jump into the water and head to the bottom lefthand corner where there will be a new island. In the middle of this island, there's a hole. Simple fall down into this to unlock the achievement.