and probably some others I've forgotten
Wing flaps and paddles.
But sometimes things just cannot be done on the water, where which brakes on land you'd be fine. I landed my flying boat into my friend's floatplane pond, which is a runway sizes slot, full of water. The wing was strong enough that I could not turn around to back taxi. There was just enough angle off of the wind that I could not sail backwards, without running the tail into shore (the rudder is delicate). Happily I do have an MT reversing prop, so I was able to back my way to the threshold, with the water rudder controlling my direction.
Seaplanes need a lot more space on the water than landplanes, which is usually fine, if you choose a larger body of water. A key element of water flying is that in most cases, the place you're going is not an aerodrome, and will have variables you have to detect and managed. And, you can land a seaplane into a lake with no land access, so if you have a mechanical problem, getting help to the plane is complicated. I have flown batteries and starters into remote lakes. And, in the worst case, you can end up floating injured
in your runway.
Water flying is wonderful, but there are many new skills and disciplines to learn. And.... the insurance companies know this!