Drive around the water if you can, ripping a skid on street tyres won't make a difference unless your tyres are dirty. Driving through the water will just put water on the track to slow you and the next couple of cars down. Let air out of the tyres, trial and error will help with how much air you need. But a good starting point would be 25PSI in the front, keep the rears high at about 40PSI to reduce rolling resistance. Beign a test and tune it should matter what your reaction tiems is, so leave the line when you are ready, not straight away, but not 10s later. You can try for reaction times, but the clock doesn't start untill you move anyway. Strip as much weight as you can. Even if that means removing your windscreen wipers and AC (the older Brisbane members will get that joke :P). Drags (at road car power levels) are all about launching and getting into second gear, after that there isn't much to it. So focus on those areas to improve upon.