The Sunlight Zone
The biggest creatures in the Sunlight Zone are Blue Whales
The blue whale (Balaenoptera musculus) is a marine mammal and a baleen whale. Reaching a maximum confirmed length of 29.9 meters (98 ft) and weighing up to 199 tonnes (196 long tons; 219 short tons), it is the largest animal known to have ever existed. The blue whale's long and slender body can be of various shades of greyish-blue dorsally and somewhat lighter underneath. Four subspecies are recognized: B. m. musculus in the North Atlantic and North Pacific, B. m. intermedia in the Southern Ocean, B. m. brevicauda (the pygmy blue whale) in the Indian Ocean and South Pacific Ocean, B. m. indica in the Northern Indian Ocean. There is also a population in the waters off Chile that may constitute a fifth subspecies.
The smallest creatures in the sunlight zone are Zooplankton
Zooplankton are small animals. Some are small enough that you need a microscope to observe them, but others you can see with the naked eye. There are two categories of zooplankton: holoplankton, or animals that spend their entire lives as plankton like copepods and rotifers, and meroplankton, or animals that are only planktonic for a short time like larval fish and crustaceans.
Strange Sunlight Zone creature: Starry Flounder
The starry flounder (Platichthys stellatus), also known as the grindstone, emery wheel and long-nosed flounder, is a common flatfish found around the margins of the North Pacific.