Abstract: A collapsible bait tank apparatus for use in combination with a water craft such as a kayak with a hull sealed from water intrusion into interior compartments for a permanent mounting or in a portable embodiment capable of transport to multiple watercraft. The device features a collapsible plastic container to hold water to maintain live bait in an aquatic environment which will maintain a watertight seal against intrusion by exterior water into the sealed interior of the water craft in a mounted mode. A hinged interior sealing ring mated to the collapsible container cooperatively engages an exterior sealing ring for a fixed mount or a hinged upper support for a portable mount. The fixed mount using the collapsible container allows a large container to be inserted into a small aperture of a watercraft and maintains a seal from exterior water entering the sealed cavities of the craft.