Hello,
It can be due to plasma which oozes out when a wound is caused by scratching. First of all, stop scratching as it can introduce infections. For these rashes, do not use any cosmetic products at the sites. You can apply some calamine lotion at the rash as it will help in soothing the skin. Also wear cotton undergarments and take some antihistaminic like Benadryl. Application of Neosporin and Bactroban helps in preventing infection and is also helpful. If the symptoms are severe then it will be best to consult a dermatologist.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
For one, it's not water, it's white blood cells. Sounds like a bug bite that was infected, thus the presence of white blood cells. Wait till it scabs and put anti-itch cream or liquid on it, I find hydrocortisone works well, then put a band-aid on it. If it swells and continues to ooze, I suggest going to your doctor, the infection may have gotten worse or you are allergic to what ever bit you.
Either way, try not to itch it, I find applying a bit of pressure or ice to it helps and it avoids breaking the skin as well.