problem is simple - tight beam can be produced only by
- small emiter die arround 1mm2 - 3mm2 MAX , that made very short list of used leds
-bigger emiter die need just bigger ( aczually deeper reflector ) or much bigger lens ( for example with big 9mm2 SST-90 you can get on relative small aspherics lens 7,5° -( on air you 'll get hand warmer in
front of light in distance 0,5m )
but these leds have low lumen output (emiter itself - not light ) to arround 450lm so must be connected in cluster with 3-4 to get some effect. ( still reflector is at least 15% more effective than any lens)
Still gets some lux readings in clear folrida or cave water , but in murky lake waters or in our Adriatic see near Gulf of Trieste .... IMO waste of time
So what's your take on the SCULA 2600 beam width ? From their website it's not clear wether it's 10° or 24° but my guess is that 24° is pretty unusable in murky waters even at 2600lm while 10° could be acceptable.
What about wreck conditions, you do not necessarily need to see far away so wider beam could be beneficial...