Different units do it differently, but the two ways I've seen it done are:
1) Karabina 4 bergans together (fire team crossing at a time) they float because of the canoe sacks used to keep the kit dry inside. Clip webbing to bergans as you don't want to drown, then push/pull them across.
2) Strip to skiddies or wear only gortex so that dry kit can be put back on the other side. Load two bergans into a bivi bag, then tie up the end, and goose neck it to make it as water tight as possible. Then float the bergans across. This method is more time consuming and problems could be caused if your contacted while crossing the river. But its gunna keep your kit and bergans drier, which makes operating again on the other side a bit easier!
There are probably loads of other ways of doing things, and I'm sure someone can rip these to shreads, but its really down to the situation.
Not sure on PTI but there is two ways of doing it with flotation packs one is with the bivi bag the other a poncho but it has been a while since we did it. if you are able to then you get out of your greens & boots & put on socks or trainers if carrying them & into gortex kit then do one of the following
Firstly you need to secure the home bank as a section basis but same principle for a platoon
1, pack your bergan & put it all in your bivibag webbing included, leave out 2 bungies & bungie the topof your bivi bag & the bottom, this allows you to have 2 hand grips if you work in paors you can carry 2 at a time, you & a buddy then make your way leaving your weapon out for safty obvously then for safety we had to tie our weapons to our poncho & tie a 3qtr full water bottle to it with 30 mtr of string.
2, take out your poncho strip as before cram your bergan full of kit & lay your webbing under the hood if you can then wrap your poncho around your kit, once done take a small stick strong about foot long & wrap the folded up bits of poncho onto around the stick & down towards the bergan then wrap your bungi around it to hold this will help create the seal.
3 first two go across one as cover one carrying the rope of you are going ot use it for helping the non swimmers etc & when they get to the other side they secure the area then tie up the rope & you have a means for people to find there way accross & the next two come accross, they can then secure the bank & the rest can follow, depending on the tac situation depends on wether you wait for all to come accross before you go to buddy buddy & get back in to greens or when the 2nd pair are accross you start to get the lads dry
commanders decision really one thing i would say depends how cold it is for the urgency to get them out of wet kit.
last thing be carefull of the monkey water ......... cause when you go in if its cold youll be making them monkey sounds who who who agh agh agh, hope this helps for flotaion packs
ERRMMM JUST GET A BERGEN (WITH YOUR KIT ALREADY PACKED IN HOPEFULLY IN THE LINERS SUPPLIED CRAP AS THEY ARE) GET A FCUK OFF BLACK BIN BAG LINER STICK THE BERGEN INIT GATHER THE OPENING END OF IT AND TWIST, GETTING AS MUCH AIR INTO IT AS POSSIBLE THE HOLD THE BUGGER FOR DEAR LIFE(ONLY JOKING) THAT METHOD WORKS FOR ME ALL THE TIME. JUST MAKE SURE ITS A HEAVY DUTY BLACK BAG NOT THE CRAP FLIMSY SORT...
UP TO U IF YOU WANT TO PUT IN ARMBAND BUT THEY TAKE UP TO MUCH ROOM AND LOOKCOMPLETLY STUPID BEING BRIGHT ORANGE SURE WAY TO BE SEEN IF THERE ON THE OUTSIDE..
wouldnt bother with those sh1te issued bergen liners, canoe bags are the way ahead. The inside of your bergen will be damp but evrything inside the canoe bag will be bone dry, especially if kits individually water proofed as a matter of course.
goretex and chinese fighting shoes/rock climbing "stickies" take up less room when youre not using them and dry quicker than trainers. Other than that its goretex to get across, tactically its up to your SOPs. Undo the sling, put the male through the carry handle of the bergen whilst it in the water then do the sling up - you can still bring the weapon to bear as it lies across the top of the bergen but you wont lose it. Mega basic but tie a knot in the excess of your sling too, in a current the sling can slacken and youd look a knobber being charged for losing your rifle in the ogin.
Safety wise use your loopline and carabiner to clip into the duty black marlow that should be taken across by the first man and tied off at both sides.
Apologies if im insulting common sense with any of this, when we practise this we usually do it with MLs and an open water lifeguard or some such qualified bloke, can be a PTI but doesnt have to be.
Make sure you can swim and comply with all necessary safety regulations.
The jungle warfare manual used to have a piece about wrapping the large pack in a poncho to make a float. I tried this on the banks of a slow-moving, 50 metre-wide jungle river and found poncho wouldn't reach around the girth of a full bergan. My alternative was to place bergan inside the heavy-duty plastic bin liner that I had been using as a waterproof liner. With the neck of the bin-liner knotted I found it easily supported the weight of the heavy bergan. Clip webbing around the bundle, buckle uppermost with ammo pouches above waterline and place weapon on top secured to bundle by long length of paracord. Push bundle in front, keeping one hand on pistol grip and trust no near-submerged tree trunk side-swipes you while crossing. There was no parental guidance available at the time...
Make sure you do it with the proper safety stuff in place .Couple of our lads nearly drowned doing a river crossing across an estury . Being rescued by mod plod is not big or clever .Sometimes risk assesments are needed for a reason .
Get your head around the regs. The safety organisation you are officially required to put in place these days is significant (you need at least four different people with three different qualifications). The Army has killed a lot of people in water in recent years (far more than on ranges). Make sure you are well read up and have the right system in place...or prepare for a very unpleasant interview with M'Learned Friends if something goes wrong.
A good point of contact would be the SO3 Light Role Recce Course working at LWC in the Recce Div. They teach River Crossing to potential instructors, have all the relevent lesson plans, but more importantly, will point you in the right direction safety wise.
As has been alluded to above, there are serious safety implications and more than a couple of lads have died in the last few years. Warm tent to change in on Far Bank and safety boat with qualled up driver are just a couple of the things that you may not have realised are now compulsory.