I swim most days in summer but don't normally disconnect for more than about an hour at a time. Pre pump I used to go very low, so now my glucose levels remain stable or just go down a little.
Longer you won't have that reservoir, under the skin hence BG going up.
I think some people reconnect and give themselves a small bolus every now and then but that's not always easy or convenient and can lead to rollercoaster levels.
There is whats called the 'untethered regime' where you use lantus/levimir as a basal but your pump for boluses ( its a bit more complicated than that, but it was designed specifically for people doing things like water sports) details here
http://www.childrenwithdiabetes.com/clinic/untethered.htm
but as you're very new to the pump, it is something you would want to discuss with your docs.
You can also have a pump 'holiday' and go back to MDI for a short time.
Perhaps others have some more ideas.
As for cleanliness, I assume that you are capping off your site for swimming, that way nothing should 'get in'. I also find it useful to put tegaderm on the site before insertion during hot weather/lots of swimming, it helps it to remain stuck.