However, posting a link to a thread where the "explosion" may very well have happened independently of the battery technology may not be "accurate" informing.
Except that's not true. NiMH batteries won't "explode" in the same sense that LiIon batteries can. Besides, the link simply shows that the maker of your light has had products explode. Note that not one but four separate Salvo incidents are referenced in addition to one reference to a LiIon explosion and you might read TobinGeorge's post on page 2. Not everyone has the knowledge and skill to understand how to make such products sufficiently safe and I'm too skeptical to take the word of a manufacturer in fire-fighting mode. It's not just LiIon that's the point here either. Huge energy storage, violent battery chemistries, lethal ballast voltages, and soft plastic enclosures with cheesy clips don't mix in my opinion.
There have recently been incidents of notebook batteries catching fire and exploding. You would think, considering the volumes in that market, that engineers would put careful thought into preventing that. It shows you the difference between LiIon and NiMH in terms of potential for catastrophic failure.
I have a bias against large LiIon batteries and I have tried to explain my reasoning. It's not important to me to change your mind. Further, I am not advocating anyone undertake a DIY project, I was simply showing what I achieved (quite a while ago) in contrast to your claim that LiIon offers much greater power in the same size package. I believe 100Wh in 3.5 pounds is pretty good achievement and it doesn't involve nearly the injury risk or any full-custom charger solution. LiIon can do better but not with off-the-shelf cells that are designed small enough to be safe in the absence of custom safety engineering.
I would still like to know the Wh ratings of those LiIon packs. Ah is not a rating of power. Airlines have restrictions on both Lithium content AND overall power and 100Wh is the largest allowed without permit. Looking at Salvo's current site, it appears they are offering packs in the 250Wh total capacity range. If those are a single pack, then technically they are hazardous cargo and you can't just stick them in your checked bags (legally).
What Craig is saying is that the Li-Ion could possible do a lot more than just stop working when flooded. It can ignite and start a nasty reaction which could end in explosion. The bigger the pack, the larger the explosion.
I was advised by my engineer whose career was LiIon batteries, charging circuits and power supplies, that my target battery size in LiIon (similar to Salvo's large packs BTW) if exposed to a total flood could very well blow me into pieces underwater. So, yes, that's what I'm trying to say!
Just because an anecdotal flood doesn't result in explosion doesn't mean it can't happen.