My current favorite summer deck shoes are Keens, but not just any keens, they have to have the correct sole.
Of all the deck shoes and sailing boots I have used over the years there is one commonality in the ones that had the best grip, and that is the Sperry Topsider style herringbone grooved soles or some variation. That is what I look for in any footwear I buy for sailing. I tried to find images online to show what I am talking about, but surprisingly, nobody seems to think showing what kind of sole a shoe has is important to their marketing! So I snapped a pic of my 3 current boat shoes; the standard "sea boot", Keens sandals, and Sperry Topsiders. All 3 of these give me fantastic grip, even on wet, 35 year old non-skid on a heeling boat. The thing all of these have in common is that they are fairly soft rubber compounds, and the grooves all open up when the shoe is flexed. It is all about surface contact, and a chunky, aggressive tread just doesn't cut it on a boat!