People with diabetes are hammered with things they shouldn't do. Always high on the list is not to go barefoot. We always tend to over-analyze such recommendations, often to our own detriment.
In our own house? Well, yes. I've pulled all sorts of crazy things out of people's feet. Pet hair, pins, staples, glass, a toothpick. No joke! Some, of course, knew that the foreign body was in there...it really hurt! There are those with diabetes who don't have any sensation due to peripheral neuropathy. These folks can step on a foreign body and not have any idea. They may notice bleeding on the carpet or in their shoe and find out that way. For others it can be days or more before they discover the problem.
The most universally accepted place to go barefoot is the beach. No problem, right? Wrong. Let me count the ways...
First of all, sand gets very, very hot. For those who have full sensation in their feet, they'll realize it and will protect their feet with shoes, flip-flops, Crocs, etc. For those who don't have sensation, they will have no idea about the heat of the sand. Severe burns can (and believe, me often do) result. If you have any decrease in sensation, always protect your feet on the beach.
Add the heat of the sand to the multitude of foreign body's unique to the beach. Seashells can be sharp and cut into the foot easily. Coral and other natural growth can scratch and do the same. This is more dangerous than your household foreign bodies. On the beach, there are bacteria that you won't find anywhere else. So along with the danger of simply stepping on something and not feeling it, you can add the risk of infection which, of course, is exacerbated by the diabetes depressing the immune system.
So the take home message is, always be careful and always protect your feet. You need to always think about where you are and what dangers may be lurking. Even in a comfortable situation, like a day out at the beach, being proactive in protecting yourself will always keep the memories of the day pleasant.