Been there.
Ten minutes swimming is lot harder than 30 minutes AquaFit. The rest of the time, just being in the pool and moving is a good warm down.
In terms of reducing, I'd decrease refined carbohydrates - white bread, pasta, pastry - and try to not have them at all for a while, as they inevitably also include high fat but don't make you feel full. Don't cut out potatoes, though, as they are a far better choice, especially baked or steamed in their skins, because they are a carb with fibre and vitamin C. Swap out any butter with soft cheese - you still get calcium, you still get richness and flavour, but just fewer calories in the process.
Refined sugars are pointless - things like fizzy drinks, sweets, cake/biscuits (but if you are not having white flour/baked goods, cake isn't on your list anyhow).
Weightbearing exercise is an injury risk (as my bolloxed lower joints and plantar fascia can testify), so don't do it yet. A five minute walk with good, supportive trainers designed for heavy runners will be enough to start with. Later on, you could look into beginners' yoga or some gym work - you could use the weights machines without any issue and the standard Concept II rowing machine is perfectly fine for your weight. Increasing your muscle mass will immediately start you using more energy in a day and if you feel stronger, you feel good and are more able to do that extra minute.
I always reasoned with myself that I'd go for ten minutes if I didn't feel like it. 'Ten minutes and I can go home'. Thing is, after ten minutes, I'd say 'another five' and by that time, I'd be warmed up, the endorphins would start and I'd feel good enough to stay longer.
Are there foods that you like that are seen as 'healthy'? Do you like strawberries, pineapple, salmon, chicken breast? Can you see yourself as having a sweet treat by buying whatever fruit you like and turning it into a smoothie with milk/oat milk, a splash of yoghurt and a banana? Or cook a piece of salmon (including the skin) in a pan and then chuck it on a massive bowl of salad and avocado chunks?
Do you like soup? If so, you don't need to have tins of the stuff which are full of dairy, fat, sugar and other additives - freshly boiled veg, a potato and good stock makes a fresh tasting soup. You could put small pieces of cooked meat into stock and add a handful of frozen veg, then top with some soy sauce and chilli flakes.
In all honesty, the things that I'd suggest you lay off at the moment are the ones that have the most ability to affect your mood/how you feel with the lowest nutrient levels - white flour, sugar, pasta, fat for fat's sake - meat and fish, fruit and veg and leaves will feed you brilliantly.
Add a multivitamin, get your vitamin D levels checked, as they're likely to be really low (and if so, take the prescribed supplements if they're so low as to need the high doses you can't buy OTC), which can affect your mood hugely.
And remember - if you are outside for five minutes in daylight, you're outside for five minutes more than you were yesterday. That's 35 minutes light exercise in a week. If you were to add in an AquaFit class and one other half hour thing (even floating around the pool on a Thursday), that's about 100 minutes of exercise in a week - or 15 minutes a day all year.