If you suspect water in the tank... either get a bottle or two of HEET in the yellow bottle (gas dryer, methanol) OR siphon off as much fuel as possible and refill with some E10 stuff if you have it around your parts. That's all I run (E10): cars, motorcycles, OPE, etc..
Second, Seafoam won't hurt anything (light oil and naphtha mostly).
Third, 93 octane is overkill for a civic... won't hurt anything other than your wallet. I'd prefer going to a gas station with a lot of traffic (fuel is fresher) and filling up with 87 octane. Most people are cheap as well, so you know 87 is consumed WAY more than 89, 91, or 93.