Because of the water, I would get pull on work boots, Wellingtons or comfortable rain boots, basically waterproof boots. I have Kamik Rangers which I love. I went on all kinds of hikes and trips around Alaska to hunt and fish with them. I don't know if they make them anymore, though. I have friends that love the old XtraTuffs. A lot of people in AK wear them all the time and are quite agile in them. I, not being agile, can't really say anything about the Kamik Rangers but they are comparable to the old XtraTuffs. The new XtraTuffs are made in China and with inferior materials so avoid those. I checked on Amazon and Rangers are $25. There's higher rated boots for $16 and the Kamik Hunters which are an improved Ranger are $43 to $70.
Edit: I should have noted that I had no problems walking across super mossy and slippery rocks, fast running rivers and creeks, and ice with my Rangers on. I don't know if that would apply to your situation but it does tell you something about their grip.