Turning a Rubber Pumpkin into a Diorama

I never had much use for fake rubbery pumpkins, but when I saw some uber cool ones at Michael's this morning that were used as dioramas, I decided I had to give it a go. So I'm going to make an underwater scene with mermaids.  So I got the white version so I could paint purple/blue over it easily. The floral consultant said to cut it with a hot knife, so I'm going to use my woodburning tool to cut out the 'sea cave'. This is going to be fun. I'll keep you posted.