I searched amazon and zappos for water shoes in wider widths than medium and apparently this is it. NB offers this shoe in D(M) and 4E (nothing in between).  I got them in D(M) for myself (I often wear women's W) and 4E for my husband.

I am not sure I would call it 4E - it is very difficult to put on and not as wide as normal shoes in 3E width, but it is definitely better than D(M). This mere fact gives this shoe an above average rate. It seems comfortable when walking at home, but I will append my review after our vacation, when we hope to use them.