Hope "fishy" problem does not become a stinky problem, perhaps it is a spawning area.
Sleeping sitting up-right never, sleeping horizontal during the day I would have to be exceptionally ill, still don't sleep more just laying down enjoying the comfort of my pillows.....
Look forward to your next walk about, it is a very pretty area.
I hope the same when it happened a few years back the smell lingered for a long time
I know many who have a nap each afternoon but like you I can only do that if I am ill otherwise it messing up my sleeping at night