Another vote for force fins. If you can try some on before you buy I would highly recommend it as they are expensive and the sizing is a little weird. You can get them used very cheap if you search craigslist. I got a pair of large force fins (regular) for $40. I wear a size 12.5 in running shoes and these were too big barefoot, and too small with any kind of bootie. I ended up buying the comfort instep for $35 and now they fit perfect barefoot. Then I found a pair of XL force fin pros for $30 on craigslist. These fit with my 5mm booties perfectly. Later I picked up a pair of small force fins for my gf who is a size 5.5 and they were a little too big for her barefoot, but fit ok with a 2mm sock.
If you do end up with force fins, here is a tip on the bungie straps. You can buy the bungee terminals for $1 a piece at bass pro shop. Then pick up some marine bungee at your local boat store for $2 or so. For $6 you have bungee straps. For the back part that fits on your achilles, you can use part of an old flip flop or even nothing if you are wearing booties.