10,000,000 bonus points:
Collect the letters in the bonus room in order to spell "JAMESPOND"

All exits opened:
Hold Left + C and power on the Genesis. Press Start and release all buttons at the title screen. Hold A + B + C and sweep the D-pad in a Full-Circle during game play.

Level skip:
Press Start + C at the title screen. Begin game play, then hold A + B + C and sweep the D-pad in a clockwise Full-Circle.

Hidden warps:

Mission 1
Save all the lobsters to enable two warps on this level. The first warp is in the seaweed next to a white rock to the left of the entrance pipe. Position your character over the seaweed and press Down to jump to mission 6. The second warp is located to the far left after saving the last lobster. Jump out of the water and land on the ledge. Move to the edge and press Down to jump to Mission 11.

Mission 2
Save all the fish from the toxic waste. Move to the right of the entrance pipe at the start of the flat ground. Press Down to jump to Mission 10.