I've worked with water zones quite a bit, and here's something interesting - there actually isn't any special water combat system in place (this keeps the gameplay focused on land-based encounters, which makes sense given the core mechanics). Your regular combat strategies will work just fine near water areas, even around places like the hydro dam.

When you're dealing with freakers near water bodies, stick to what works - molotovs are still your best friend for crowd control, and shotguns remain reliable for close encounters (this is because fire mechanics and damage values stay consistent across all terrain types). Something worth noting is that screamers should always be your priority targets, even in waterside encounters, because they'll still call in reinforcements just the same.

Here's something that might help - while you're around water areas, try mixing up your approach between stealth and direct combat, just like you would anywhere else. The freaker ai doesn't change its behavior patterns near water, so you can use this predictability to your advantage (especially helpful when planning ambushes near riverbanks or dam structures). And remember, those environmental objects like planks and axes work just as effectively near water as they do anywhere else in the world.