What is a potential risk when departing over large bodies of water without in-flight refueling capability?

When departing over large bodies of water without the capability for in-flight refueling, one of the significant risks is being outside gliding distance to a suitable landing site. This situation can arise because, if the aircraft loses engine power or encounters severe mechanical failure over water, the pilot might find themselves unable to reach land for an emergency landing. Water does not provide a suitable landing surface, and the distance to land can be extensive. Therefore, the risk assessment must always factor in the range capabilities of the aircraft, particularly when the flight path leads over vast stretches of ocean or large lakes, where unplanned landings on the water are not feasible.

The other options, while they may represent possible issues in flight, do not directly address the critical safety concern associated with flying over expansive water bodies without the ability to refuel mid-flight. Forced undercarriage landings, navigation difficulties, and higher fuel consumption might be relevant in certain contexts, but they do not specifically encapsulate the immediate existential risk faced if the aircraft encounters an emergency far from shore. Thus, being outside gliding distance to a suitable landing site is the primary concern that arises from this scenario.