A modular backpack system includes a personal floatation harness having an automatic inflator mechanism and pack attachment features; and a plurality of pack modules selectively attachable to the pack attachment features to form a floatation-enhanced backpack. Each one of the plurality of pack modules may further include a different arrangement for accommodating accessories. For example, the different arrangements may include arrangements having different compartments. Other arrangements may have different attachment features. The different attachment features may include different lash points. The backpack module may be one taken from the list of: a pack adapted for kayaking with a waterproof compartment and lash points for ready access to accessories; a pack adapted for sailing with waterproof and non-waterproof compartments; a pack adapted for hiking with multiple compartments for tools and supplies; and a pack adapted for everyday carry (EDC) having multiple quick-access compartments for carrying everyday tools.