Using a boat, it's possible to craft and use fireplaces in the middle of the ocean.

https://www.youtube.com/watch?v=OhnQkuptrM0

• Fireplace can be crafted and ignited on boat
• Fireplace still appears to work as normal, giving heat to player and causing damage when too close
• Fireplace has collision and the boat can become temporarily stuck/be stopped when driving into them
• Gas stove can also be dropped outside the boat and be turned on while floating on water