Near fresh water places are hard to live in, yet both the salmon and the platypus manage it. They solve the same problem in different ways.
The salmon lives in the oceans and the rivers that flow into them. It is about 70 centimeters long for many kinds. It has a strong, muscular body, which lets it swim upstream and leap up waterfalls. It is a carnivore and eats insects, shrimp and small fish.
The platypus, by contrast, lives in rivers and streams in eastern Australia. It is about 50 centimeters long. It has a soft bill that senses tiny electric signals, which lets it find prey underwater with its eyes, ears and nose shut. It is a carnivore and eats insect larvae, shrimp and worms.
Both animals show that there is more than one way to survive in a near fresh water place.