Aquarist is a casual simulation game where players manage aquariums and an aquarium shop. Players create and customize homes for diverse marine life, including fish, sea turtles, sharks, and octopuses. The game involves fulfilling client tasks, using rewards to expand the business with new species and locations, and caring for both freshwater and saltwater creatures. Expeditions to discover new species and treasures, alongside varied client projects like art museum tanks or kitchen decor, add to the gameplay.

The simulation allows for detailed aquarium customization, including the use of personal photographs as backgrounds. Players care for numerous species, ensuring their health and happiness through environmental control. The scope extends to running an aquarium shop, expanding to locations like an exhibition and an oceanarium, and undertaking a variety of client commissions.