1, species difference: chocolate dolls are freshwater ornamental fish, while submarines are seawater ornamental fish. Chocolate dolls and submarines have different habitats and adaptability.

2, appearance difference: chocolate doll's body is round, the back and abdomen are brown, there are black spots on the body, small eyes, triangular mouth. The submarine fish has a long body, green back and abdomen, black spots on its body, big eyes and crescent mouth. The appearance characteristics of chocolate dolls and submarines are obviously different.