If you want to keep shells and most all the sand out, try O'neil super freak 2mm tropical surf booties/shoes. Have yet to find any "shoe" that performs anywhere near as good as them and you can still swim fine with them (try that with diving booties,, and yes I'm a diver also). Their only weakness is that if you walk alot on asphalt n rocks, the soles aren't all that thick, due to being made for surfboarding etc. I have a few pairs that I rotate in use and I use them hundreds of hours a season. One of the best gear "discoveries" I found several years ago, during the never ending search for somethings-gotta-be-better for footwear detecting.