RE: Help! On vacation laptop won't turn on water may be involved. Getting 3 beeps
Three beeps is a mainboard failure. Unfortunately, if there's evidence of water damage, it'll be deemed accidental damage and the warranty won't cover the repair.
You'll need to contact Dell support - but if it's a sub-$700 system to begin with and it's considered accidental damage, the repair needed won't be cost-effective -- it'd be better to replace the system than repair it.