We did a boat-based tour, even fearing seasickness a bit. It wasn't so bad, and I was the only sick once. Accommodations onboard were basic but clean: small cabins with private toilet facilities (not all of the cheaper boats have these).

Three meals a day are included, and these are good and varied. Water and juice is also included in the price, and alcoholic beverages are available at reasonable prices.

My recommendation would be to not go for the cheapest boat (generally called tourist-class). You are going to be in transit on the water a lot, and you only get as good as you pay for. I have heard a lot of horror stories about the cheaper boats!