The most curiously beautiful moment of a heartbeat is not the beat itself, but the silence between beats. What happens in this liminal void? And what happens to this void when different sounds from the environment affect it? Initial research conceptualized the heartbeat into a series of pebbles, orchestrating them with reflection and shadow as a way of understanding the in-between. This project avails the duality of the heartbeat as its lens for the design of a Marine Bioacoustics Research Facility and Art Installation Space. The fluidity of the In-Between choreographs a set of environments inspired by that intriguing moment of silence before the next.