Create a serene depiction titled "Serene River Harmony," representing a Bangladeshi river scene in fluid, abstract forms. The river should flow diagonally across the design in soft gradients of blue and green, surrounded by minimalistic depictions of trees and small boats. The boats should be outlined in bold black, creating a striking contrast against the flowing colors. The abstract composition should convey a sense of peace and natural harmony while maintaining a clean, modern look. The design should feature a transparent background, making it ideal for apparel printing.