Sinuous swimmers refers to eels, which are elongated fish that inhabit both freshwater and saltwater environments. They have a snake-like body shape and are known for their ability to swim in a sinuous, or winding, manner. Eels are found in many parts of the world, and some species can grow to be quite large. They are an important part of many aquatic ecosystems, providing food for larger predators and helping to keep the water clean.