Capacity gets issued while you are moving, which is why the edge of anything never feels survivable from the edge.
Water that would drown a person standing ankle-deep at the bank carries them a thousand cubits in, and nothing has changed about the water. Each measured advance builds exactly what the next depth requires, so the belief moves from this will take me under to this will hold me, the state steadies, and the steadier state makes the following thousand possible.
The river pours out of the sanctuary and it does not rise for anyone admiring it from dry ground. Depth is granted to the walking. Waiting at the shallows for proof of buoyancy keeps a person ankle-deep for life, skilled only at what the shallows ask of them.