let me chime in as a (former) TypeII.
Go keto, seriously. Below 30g carbs. You should be giving your pancreas a rest from producing, and your body from getting wacked by insulin. do it for 30 days. This will help you get your sensitivity back. THEN, go for a really hard swim (it seems what you like) harder than you normally would, then start adding in starches. Not a lot at once, slowly up the (primal) carbs/starches to around 100G.
How you might ask?
Meat, fish, Fowl (as much as you can pack in!)
Green veggies roasted/sauteed in FAT.
BAS with protein/fat
Just a suggestion from someone who has been there.