I don’t understand why watermelon doesn’t have plural form in this sentence :

I am making a fruit salad. I am mixing mangoes, watermelon and oranges.

If I made the watermelon in plural form, would it sound unnatural? Correct me if I am wrong. Thanks.

I don’t understand why watermelon doesn’t have plural form in this sentence :

I am making a fruit salad. I am mixing mangoes, watermelon and oranges.

If I made the watermelon in plural form, would it sound unnatural? Correct me if I am wrong. Thanks.

I don’t understand why watermelon doesn’t have plural form in this sentence :

Mangoes, watermelon and oranges.

If I made the watermelon in plural form, would it sound unnatural? Correct me if I am wrong. Thanks.

I don’t understand why watermelon doesn’t have plural form in this sentence :

I am making a fruit salad. I am mixing mangoes, watermelon and oranges.

If I made the watermelon in plural form, would it sound unnatural? Correct me if I am wrong. Thanks.