Although the marine biome’s temperature varies greatly from location to location and with depth, the average temperature is about 39 degrees Fahrenheit. This takes into account samples from all five major oceans at various depths.
This is colder than most would expect and is only a few degrees over the freezing point. While many of the world’s oceans receive great amounts of sunlight, the sun’s heating rays only heat the upper layers of the water. The deep water is very cold, regardless of its position on the globe. These low temperatures help to reduce the average temperature of the entire biome.