[10] However, the streamlined body plan reduces friction and drag in the water and allows sea turtles to swim more easily and swiftly.

Fossil evidence of marine turtles goes back to the Late Jurassic (150 million years ago) with genera such as Plesiochelys, from Europe.

This species inhabited the oceans covering Europe in the Late Cretaceous and rivaled the concurrent giant protostegids such as Archelon and Protostega as one of the largest turtles to ever exist.

[27][28] Below is a cladogram showing the phylogenetic relationships of living and extinct sea turtles in the Chelonioidea based on Evers et al. (2019):[29] †Toxochelys †Protostegidae †Corsochelys Dermochelyidae †Nichollsemys †Allopleuron Cheloniidae †Argillochelys †Procolpochelys †Eochelone †Puppigerus †Ctenochelys †Peritresius †Cabindachelys An alternate phylogeny was proposed by Castillo-Visa et al. (2022):[26] †Toxochelyidae †Protostegidae †Corsochelys †Eosphargis Dermochelys †Nichollsemys †Leviathanochelys †Allopleuron †Procolpochelys †Argillochelys †Eochelone †Puppigerus †Cabindachelys †Ctenochelys †Peritresius Natator Eretmochelys Chelonia Lepidochelys kempii Caretta Lepidochelys olivacea Sea turtles can be found in all oceans except for the polar regions.

A study conducted on this topic shows that body size is positively correlated with speed, so larger baby sea turtles are exposed to predators for a shorter amount of time.

In 1987, Carr discovered that the young of green and loggerhead sea turtles spent a great deal of their pelagic lives in floating sargassum mats.

In the open ocean, pre-juveniles of this particular species were found to feed on zooplankton and smaller nekton before they are recruited into inshore seagrass meadows as obligate herbivores.

Salt gland functioning begins quickly after hatching, so that the young sea turtles can establish ion and water balance soon after entering the ocean.

[54] However, leatherback sea turtles (family Dermochelyidae) are able to maintain a body temperature 8 °C (14 °F) warmer than the ambient water by thermoregulation through the trait of gigantothermy.

According to Gruber and Sparks (2015), fluorescence is observed in an increasing number of marine creatures (cnidarians, ctenophores, annelids, arthropods, and chordates) and is now also considered to be widespread in cartilaginous and ray-finned fishes.

[65] Light availability decreases quickly with depth, and is refracted by the movement of water when present, celestial cues are often obscured, and ocean currents cause continuous drift.

[66] Passive drifting within major current systems, such as those in the North Atlantic Gyre, can result in ejection well outside of the temperature tolerance range of a given species, causing heat stress, hypothermia, or death.

[66][65][67] Specific migratory routes have been shown to vary between individuals, making the possession of both a magnetic map and compass sense advantageous for sea turtles.

[70][71] There are three major theories explaining natal site learning: inherited magnetic information, socially facilitated migration, and geomagnetic imprinting.

[67] Some support has been found for geomagnetic imprinting, including successful experiments transplanting populations of sea turtles by relocating them prior to hatching, but the exact mechanism is still not known.

Omnivorous turtles may eat a wide variety of plant and animal life including decapods, seagrasses, seaweed, sponges, mollusks, cnidarians, Echinoderms, worms and fish.

Key findings from an experiment reveal the following in regards to the larynx morphology: a close apposition between the linguolaryngeal cleft's smooth mucosal walls and the laryngeal folds, a dorsal part of the glottis, the glottal mucosa attached to the arytenoid cartilage, and the way the hyoid sling is arranged and the relationship between the compressor laryngis muscle and cricoid cartilage.

[93] J. R. R. Tolkien's poem "Fastitocalon" echoes a second-century Latin tale in the Physiologus of the Aspidochelone ("round-shielded turtle"); it is so large that sailors mistakenly land and light a fire on its back, and are drowned when it dives.

[94][95] Beach towns, such as Tortuguero, Costa Rica, have transitioned from a tourism industry that made profits from selling sea turtle meat and shells to an ecotourism-based economy.

Eggs, hatched or unhatched, and hatchlings that fail to make it into the ocean are nutrient sources for dune vegetation and therefore protecting these nesting habitats for sea turtles, forming a positive feedback loop.

[4][110] However, the usefulness of global assessments for sea turtles has been questioned,[111] particularly due to the presence of distinct genetic stocks and spatially separated regional management units (RMUs).

[112] Each RMU is subject to a unique set of threats that generally cross jurisdictional boundaries, resulting in some sub-populations of the same species' showing recovery while others continue to decline.

[113] For example, as at August 2017, about 69% of studies using stable isotope analysis to understand the foraging distribution of sea turtles have been conducted in RMUs listed as "least concern" by the IUCN.

[131] A 2010 United States National Research Council report concluded that more detailed information on sea turtles' life cycles, such as birth rates and mortality, is needed.

Large aquatic carnivores such as sharks and crocodiles are their biggest threats; however, reports of terrestrial predators attacking nesting females are not uncommon.

[142] However, some relatively inexpensive changes to fishing techniques, such as slightly larger hooks and traps from which sea turtles can escape, can dramatically cut the mortality rate.

Light pollution from beach development is a threat to baby sea turtles; the glow from city sources can cause them to head into traffic instead of the ocean.

[149] Another danger to sea turtles comes from marine debris, especially plastics, such as in the Great Pacific Garbage Patch,[150] which may be mistaken for jellyfish, and abandoned fishing nets in which they can become entangled.

One rescued sea turtle, named Nickel for the coin that was found lodged in her throat, lives at the Shedd Aquarium in Chicago.

Lastly, the long distances and inter-ocean travel these sea turtles swim throughout their lifetime offers the perfect mechanism for dispersal of barnacle larvae.