Meet FiFish Atlantis: a remotely operated underwater vehicle that lets you capture underwater video. It has an illumination system, and an underwater control and communication system. This ROV can go down to 100 meters and navigate in any direction freely. The battery lasts for 2 ours on a full charge.
FiFish Atlantis has a slim body and can be carried easily. It can work as your companion underwater. More information is available here.