This sounds like the problem i have with my 93 trooper LS right now.
I had a wild hair on my *** and decided to take it off-roading on a friday night. So a few mud puddles and 40 minutes later I started heading back to my house when i noticed the interiour lights/gauges flickering, especially when i applied the brakes. got home fine and called it a night thinking i would take the trooper to get it washed tomorrow. next morning though, the trooper would hear nothing of it. it wouldn't crank or turn over at all. all power was lost as well, nothing worked, no lights no radio came on nothing.
anyways i had a friend try to give me a jump thinking maybe it was just a dead battery, nope. with jumper cables attached all it would do is crank/turnover once and stop. I'm lost, i'd hate to go out and start buying parts to a problem i can't single out.
any ideas? like your truck, Maytime, it sounds like my starter may have died and killed my batter as well somehow. i don't doubt some of the water i got all up in there could have done that.