The Casio Logosease Underwater Two-Way Radio features:
Underwater two-way radio (LGS-RG 005BA) by Yamagata Casio
Two units per set
Color: white
Microphone: bone conduction microphone
Speaker: Magnetic-type bone conduction speaker
Size: 89 x 41 x 44.8mm (3.5 x 1.6 x 1.8") (each)
Weight: around 107g (3.8 oz) (each)
Usage temperature: 0°C-40°C (32°F-104°F)
Ultrasound: 1 channel 32KHz USB, 4KHz SSB-AM basis
Power lasts for up to 3-hour dive (if used around 10% of time for transmitting)
Works up to 40 meters (131 ft) underwater
Range: 50-100m (164-328ft)
Voice is quieter with distance
Divers must be facing each other
Power: 560mAh Li-ion battery, charge by USB
Charging: around 2 hours
Instructions: Japanese (but Casio Yamagata has FAQ and other information online in English)
In Japanese waters there are no restrictions on using ultrasound but please check laws in other countries before using