I've used a Sunday Afternoons hat for a couple of years now, and it's a pretty amazing hat. The 4" brim provides great coverage even when the sun is coming in at low angles, and the fabric drape at the back keeps my neck protected too. It floats, in case you lose it while on the water, but don't expect it to repel rain. Light showers, sure, but not any extended wet weather. It's a sun hat, after all.
Ventilation is decent, but you'll still get a hot head if you're working hard while wearing it (same with any hat). Despite the wide brim, wind hasn'nt been a problem. With the chin cord cinched down it stays on well.
When the sun is shining though, this is my go-to hat.