Polar Ice Cap Melting or Sinking Terrain?

I am a newbie and I created an Island with terrain that started at 1.5 and with water that was 1 deep. When I hit play the island begins to sink and eventually disappears under the water HELP!

I removed the waterPro and now it is simply the camera that moves up to infinity. I suspect that it is something to do with the fact that when I open my world I get a “Scene is missing full screen camera” message. How then might I resolve this? Can I reset my Main Camera somehow or can Ii deleted and re-add it and, if so, how?
Thanks for your help.