The term 'Colorful Swimmer' can be solved by two crossword solutions: OPAH (4 letters) and Tetra (5 letters). An OPAH is a large, colorful fish found in the Pacific Ocean. It has a round body and a large, fan-like pectoral fin that it uses to swim. A Tetra is a small, brightly colored freshwater fish found in tropical regions. They are popular aquarium fish due to their vibrant colors and peaceful nature.