It looks like it is almost the opposite of cave diving [1]:
> As the name suggests, blackwater dives are carried out at night. They are typically conducted over extremely deep water. Before the dive, powerful lights are hung beneath the boat, simulating moonlight and attracting creatures from far and wide.
> Each diver is individually tethered to the boat via a rope that’s clipped to their BCD. Divers descend along their line (usually no deeper than 20m/66ft) then simply hang out and watch the show. Not all operators will tether divers to the line – some will have a set distance from the light that divers must stay within. This will depend on local conditions such as currents.
> As the name suggests, blackwater dives are carried out at night. They are typically conducted over extremely deep water. Before the dive, powerful lights are hung beneath the boat, simulating moonlight and attracting creatures from far and wide.
> Each diver is individually tethered to the boat via a rope that’s clipped to their BCD. Divers descend along their line (usually no deeper than 20m/66ft) then simply hang out and watch the show. Not all operators will tether divers to the line – some will have a set distance from the light that divers must stay within. This will depend on local conditions such as currents.
[1] https://www.girlsthatscuba.com/blackwater-diving/