In keeping the old adage, "if one is good then two must be better" a second light will indeed provide approximately twice the illumination of a single of the same output.
The UXLG-1-PRO package offers a full 12-watts of illumination stepped from one of 8 levels.
LED's also make the most efficient use of energy.
4 x AA batteries will run each light at full power for 1.5hrs, roughly two dives.
And if you're only interested in "seeing" the wonders of the sea beneath the waves, easily convert a light to a handheld.
Versatility and function, a combination hard to beat.