The shallow-pond rescue starts with an apparently easy duty: prevent grave harm when doing so costs little. Singer-style arguments then ask whether comparable help becomes optional when the beneficiary is far away. The challenge moves from a vivid emergency to the scale and persistence of unmet needs.
The rescue is persuasive partly because the need is serious, the intervention is clear, and the cost is modest. Moving to distant assistance asks which of those features remain and which require evidence. Physical distance by itself may do little argumentative work, whereas uncertainty about effectiveness could matter substantially. This distinction prevents two shortcuts: assuming every gift equals a rescue, or assuming that less vivid suffering creates no obligation at all.