http://www.batterystuff.com/kb/articles/battery-articles/lithium-battery-overview.html

I don't know what type of Li batteries were on that boat, or whether they were the cause of the fire. If they were LiFePO4, which are the common ones used in vehicles/boats, then it is very, very unlikely they themselves were the cause of the fire - overcharged or not. More likely is a short of some type. The energy density of these batteries and their ability to deliver that energy pretty much in an unlimited wholesale dump makes an unfused short very dangerous. Much more so than typical lead acid batteries.

Most consumer electronics and electrics now use Li-polymer batteries. Boeing uses Li Cobalt Oxide. Both of these have fire potential and specific, narrow charging regimens. Again, electric cars and boats typically use lithium iron phosphate - a different and far safer chemistry.

Mark