Water in Belmopan and other large towns is treated, but other water sources are questionable. It is not recommended that you drink river water, although this is the principal water source for many rural people. This is an academic course. Come prepared to take notes, keep a journal, record data, sketch, write letters and take exams. Small stitch bound or stapled notebooks are handy as journals and field notebooks.
Laundry detergent Get an environmentally friendly detergent.
You will not need a whole box. You may just want to put a few cups in a secure container. As already mentioned, insect repellant is an important item. Deet products tend to work the best, but is skin absorbent. Deet can be applied to clothes rather than skin and, when used in conjunction with a long sleeve shirt and long pants, often does the job.