Pretty much, the use of the CoC Combat Swimmer addon has been fairly limited due to the fact that the AI still refuse to enter the water even while wearing the gear. There is a script that allows AI to swim with the CoC addon,
but it requires the leader of the group to be a human player. I'll post a link for that script below.
http://www.ofpec.com/editors/browse.php?browseon=&browsewhat=-1&category=-1&subcategory=-1_-1&numreturn=25&displayformat=0&ofpv=1&searchstring=CoC+Scuba+AI+Script&searchwhat=2&searchlevel=1&searchopts=This is a discussion that is sort of mixed between Addon ideas and Mission ideas, because it talks about an addon as well as new mission ideas. So I guess this topic could go in either area.
I think the reason there have been few or no missions that use the SCUBA insertion technique is because many mission makers see little need for it. You have two choices that I can think of right off hand. First, you can start the mission with the player and any team members in the water or in a craft to be inserted into the water, and then using the mentioned script have them swim to shore where they begin their mission. And second, you can just start the mission with the soldiers already on the shore, with a simulated SCUBA insert using a variety of intro and cutscene techniques coupled with starting object placement.
Since using the diver addon is kind of boring, just "swimming" at a slow speed until you get on shore, most mission makers might see the first method above as being unnecessary. If you were to use the simulated method, by showing the diver units para out of a plane into the water or debark a boat into the water, you have the option to start the actual mission with the player or other units in a different soldier type. This will help realism in the mission a bit, by allowing the player to run the mission in a SEAL BDU uniform, or what ever soldier unit you want. I don't think a SEAL would insert onto land and continue on while still wearing his SCUBA gear.
I can see how this type of insertion would make for some interesting missions, but I have not seen any mission like this myself. I might just make one later just to give it a try.