Safety

The former (or both). It also serves as a visibility aid. A big risk is being hit by a boat. But if you have to swim alone, there are many other safety steps you should take. I respectfully suggest that you Google swimming alone in open water for discussions like this forums.usms.org/showthread.php and others.

Yup to the ISHOF. You might consider putting your keys in a separate baggie inside the bouy as well because they do tend to still get wet. Also be sure to wear a bright cap as additional safety. I also swam alone on occasion. When I did, i'd always leave a note on my dashboard saying what time I'd be in the water, the general direction I'd be heading and when I'd be out, roughly in case something happened. The other thought is to text/phone a friend with the same swim plan so that if they didn't hear from you by a certain time, to alert authorities to go looking for you. Thankfully, never had issues.

I use the buoy like the ISHOF one. It's easy and you hardly notice its there. It may be a little morbid but I figure if something did happen to me at least they'd be able to recover my body.

Based on recommendations from this forum, I use both a swim buoy and and a high visibility colored swim cap of different color. If one color doesn't show well the other might. My swim buoy is yellow and my cap is neon pink

I use a buoy (but got the English brand with heavier material) and wear a bright cap. I also have a waterproof UHF marine radio in my buoy so I could contact the beach lifeguards, the lifeguard boat, the USCG or anyone monitoring Ch. 16 if need be. (I predominantly swim in LA County where beaches are staffed year-around and there are Bay Watch boats for rescue purposes as well.) My swim watch could be used to provide my lat/long as well.