Custom emitters, custom driver
Mobula carries its own 532 nm LED arrays, recessed into the hull facets in clusters so the beam pattern covers the water above the vessel rather than a single narrow spot. Behind them sits a purpose-built driver circuit that switches the emitters between 5 and 10 MHz.
That switching speed is the entire point. An LED you can only blink slowly is a signal lamp; an LED you can modulate in the megahertz is a data link. The circuit is being designed and built in-house alongside the vessel, because nothing off the shelf does this at the wavelength and rate the mission needs.
The drone closes the loop
The submarine runs shallow and points its emitters up. The drone holds station overhead, watching the water for the signal and carrying it onward to the shore station. Mobula stays under; its link stays open. Neither half works alone — that is why the aircraft is built into the hull rather than bolted on.