Theo - by comparison, it is better to use a boat compared to swimming when placing an airstone in 50 F water
I would have found a way to make a quick homemade boat/raft.
Actually placing the airstone could have easily waited until the water temp was a more comfortable 60F-65F. Stratification is usually not strongly set or established at 60F. Layers can still be fairly easily mixed at around 60F. Main depending factors are depth, size of diffuser, air flow volume, size of pond, and volume of deep unmixed layer which all affect turnover rate. Usually a small pond such as yours less than one acre does not have a real voluminous, deep unmixed layer compared to the volume in the mixing epilimnion layer. Thus it does ot take an unusual amount of energy to mix a small pond when the epilimnion is 60F. Plus from ice out to 60F the "hypolimnion - thermocline" or deepest layer has not had enough time in most cases to form anoxia. Anoxia of deepest layer at least in OH ponds does not set in until around 70-75F at the surface.
