Translation:The bear's cub is waiting in the water; the fish are coming.
I will definitely not remember any of these offspring terms for various animals, and I'm OK with that.
For bears, the term is "bocs". "Medvebocs". Cats, dogs and the like have "kölyök". In the possessed form: "kölyke".
Other animals have various offspring, too many to list.
Generally the plural of fish is fish (five fish for example). The English sentence would sound better if it were "fish" instead of "fishes". The only time I would maybe use "fishes" is if I wanted to stress that there were different species of fish.