>>5476113As you can see in this schematic, clearly not written by a seven year old, this area of water lacks decent albedo, is the compartment that holds most of the water and it's WARM, compared to the other water(s). This meants that this place is the one with the crew and the rest isn't, because living creatures need the water to e somewhat warm and/or they produce heat themselves.
My vote is:
>Fire at the compartment pointed at by pic related. BOILED CREWMEN FOR DINNER 