Explanation: Equipment for radiotelephony use in survival craft stations under GMDSS (Global Maritime Distress and Safety System) is designed for critical emergency communication in harsh conditions. * **Operation on Ch-16:** This is the international distress, safety, and calling frequency for VHF marine radio (156.8 MHz). GMDSS regulations mandate that survival craft equipment must be capable of transmitting and receiving on Ch-16 to facilitate communication with rescue vessels and aircraft. * **Watertight:** Survival craft operate in marine environments where exposure to water is inevitable. Being watertight ensures the equipment remains functional and reliable in adverse conditions, which is crucial for distress signaling. * **Permanently-affixed antenna:** In an emergency, time is critical, and conditions can be chaotic. A permanently-affixed antenna eliminates the need for assembly, prevents the antenna from being lost, and ensures the radio is immediately ready for use. All three characteristics are essential design requirements for effective and reliable emergency communication from a survival craft.