Engine management light after puddle

Drove through some puddles today and fanbelt went squeeky, still a little noisy but it will dry off, parked up for an hour or so, i just nipped the shop in the car now and when i started it the engine light stayed on for approx 2 seconds after startup and then went out, didnt do it when coming out of the shop and car seems to drive normal.

Any ideas what could of caused this anyone? Many thanks.

Possible wet crankshaft sensor, long run dried it out. Problem solved. Many thanks for all your expertise, etc.