Laptop shutting down when making big map with ocean

Hello there. I’m making a big map with ocean, and my notebook makes loud fan noices, overheats and then shuts down. How do I reduce FPS, or speed at which rendering goes? I’m ready to make rendering or compilling shaders go slower.

My notebook specs:
2 core Intel Core i3 5th generation CPU
AMD Radeon Graphics HD 8750M
4 or 6 GB RAM
732 GB HDD