Check out the latest product from TTF. It's a Stingray and Jellyfish Sting First Aid Kit. It's full of all the stuff you need to treat either injury - right down to a heat bar to help soothe the pain of getting nailed by a 'ray. It's only 12-inches tall and 6-inches wide, so it should be no problem stuffing this in a boat hatch or in a kayak.
The bag is also waterproof and re-sealable, so it can be used as an emergency ice bag, or even a dry bag. This is sorta' one of those "just in case" items. You hope you never have to use it, but if you do, at least you know you've got the stuff to doctor yourself up until you can get some help.
We also have a new Jellyfish Sting Relief Gel. You basically spray it on and then scrape it off. The gel bonds to the nematocysts (stingers) that jellyfish leave buried in the skin and when you scrape the gel off, the stingers come with it.
There's full info on the kit, including all the contents,
HERE.
Retail price should check in somewhere around $25.00.