Starts fine then barely runs, then after one day runs fine?

I recently bought a 1997 Jeep Cherokee XJ as a work vehicle. Motor is rebuilt and has approximately 8,000 miles on it. I started it up one day and it started like normal, then once I started driving it it kept wanting to quit and did a couple times. I thought at first it could be the fuel pump, then after letting it sit for a day it ran perfectly fine. If it was the fuel pump wouldn’t it be doing this constantly?Could it have been water in the gas?? I have been playing on it a little bit, including driving through lots of mud pits and puddles. Anyone think it could be anything else besides water in fuel??