Waves observed on the ocean surface often nonlinearly interact among themselves and undergo algebraic growth – a mechanism known as resonant triad interaction. Bragg resonance is a special resonant triad in which one of the constituent waves is the ocean's undulating bottom boundary. Here we show that, in the presence of an ocean current, two surface waves or a surface wave and an interfacial wave (wave existing at the ocean pycnocline) can undergo exponential growth.