If you’re going to be fishing on the edge of the water then buoyancy is going to be a nice added extra to your jacket but these aren’t unsafe places and the main aim of a fishing jacket is to protect you from the elements.
If you’re going to be on a boat, fishing from a kayak or any fishing activity where you’ll be on the water then buoyancy becomes a much greater issue if you were to fall in. If this is going to be you then one great option is to buy a fishing life jacket as this will be able to act as a normal life jacket but will all the pockets and features that you’d want from a fishing jacket.
If you’re on the water though then you could simply get a normal fishing jacket and then just make sure that you have access the best life jackets possible in case of an emergency. Buoyancy in a regular fishing jacket is not that important as you should never be in life saving situations but it’s always a useful extra feature to have.