I'm sorry, Crowley, but I am going to take issue with your statement about imodium. It was once, indeed, medical doctrine to avoid the use of antidiarrheals, on the theory that it just kept toxins in the gut. That view has changed. Antidiarrheals can help prevent dehydration, by making it a little easier for patients to keep up with their fluid requirements orally. They are now routinely used in everything except autoimmune colitis.
As far as prevention goes, I don't have anything to add. Avoiding anything that hasn't been peeled or boiled, and anything that has been washed in tap water, might help. But I was more careful on our Egypt trip than I have ever been anywhere, and I got sick anyway (as did almost everyone on our trip). Pepto Bismol did not seem to work very well (which suggests it is not toxigenic E. coli, as the bismuth binds and inactivates the toxin from that bug) nor did Antinal help anyone. Cipro, however, did.
I would go to your family physician and get the following prescriptions: 5 days of Cipro and 2 days of Phenergan pills (or suppositories, but most people seemed to have more trouble with diarrhea than with vomiting). I would pick up a couple of packages of Imodium (which is OTC) and Pepto Bismol tablets (which won't hurt anything, and might help). The Pepto should be used as a prophylaxis, and requires at least two tablets four times a day to be effective.
Good luck with this. I have wonderful memories of our boat time, but the rest of the trip is seen through rather jaundiced eyes. It is NOT fun to be a tourist with turista in a country with no public restrooms . . .