Here is a fully expanded boathouse which you can see is out fishing. You can also see the magnifying glass, if you click on that you will be able to search on your maps.
This is your map, it doesn't matter how many items you find. You will only ever have room for three items to bring back. So choose carefully. I usually choose GR CASH and Keys first, then speedups, then collection items. I seldom choose coins or decor as I have tons of both and I don't really decorate my ranch too much as it slows down my loading time.
When the boat returns this is what the final screen looks like
I usually opt for the long fishing trips because those fish almost always give me GR cash and keys every time I send it out.