Diamondback terrapins are similar to freshwater turtles but they live in brackish water of varying salinity.
A young diamondback terrapin (Malaclemys terrapin) offered for sale on a reptile expo.
Diamondback terrapins are still relatively common but once they were a lot more abundant in North America — unfortunately people ate most of them
Diamondback terrapins can be kept as pets, they require a setup similar to other aquatic turtles. Diamondback terrapins do prefer brackish water but they will survive in fresh water. Terrapins should not be kept in pure seawater since they need something more dilute to drink. Diamondback terrapins require basking lights for heat and UVB, and the need good water filtration.
Diamondback terrapins are carnivorous and they tear pieces off their food while eating instead of swallowing it whole and tend to create a mess. Captive bred diamondback terrapins will take prepared food for aquatic turtles, some wild caught specimens will however require feeder fish. In any case as with all pets would be owners should try to get a captive bred diamondback terrapin as a pet, not take one from the wild.
Further Readings:
Diamondback Terrapin | Basic Facts About Diamondback Terrapins on Defenders of Wildlife.
Diamondback terrapin videos, photos and facts – Malaclemys terrapin on ARKive.
Terrapin Care.
Care Sheet for Diamondback Terrapins.