No, it is not Somogui. That would be due to previous HYPOglycemia through glucagon peak and very quick synthesis through liver storage of glycogen (takes a few minutes, intended for severe stress). It is gluconeogenesis + PERIPHERAL insulin resistance.
Diabetes means no insulin - either not enough of molecules, or enough but for some reason they do not work where and how they supposed to be. Either way, it means that, doesn't matter how much glucose you have in blood and how it got there, it stays there. With no insulin, it cannot get into cells and be used.
You woke up, started to do things, then swam. Your muscles (the biggest eaters of glucose overall) asked for energy, so your liver listened and made some glucose. Muscle glycogen was one source, another one was fatty acids from your body fat through aceCoeA going into gluconeogenesis and amino acids through piruvate (for knowing which one prevailed, it is needed to know your body physiologic characteristics like age, gender, % body fat, etc, but it is not, in fact, that important). The process, unlike "quick" gluconeogenesis from liver glycogen, takes 30 min at best and probably longer. The problem is that you still do not have insulin to use that newly made glucose, therefore it just swims in blood and eventually gets mostly peed out. It is made, but cannot be delivered where it is needed when it is needed.
Peripheral glucose receptor uptake activator like metformin and vicious fight with insulin resistance (diet, exercise, stress reduction, repeat) will help.