I am a big believer in body armour. ...In addition to running rivers, I ride both street and dirt bikes.
I have been wearing body armour on the river for a few seasons
IMHO most dirt bike specfic armour only works ok on the river...the problem with type of armour is that primary impact protection comes from hard plastic, if ypu were to wear this gear under your splash-dry gear...it would destroy your expensive gor tex gear, from internal abrassion, so it most be worn as an outer layer....the problem with this is two fold the velcro that holds in place could be riped open by current, and you lose the gear...or it could catch the current and make the swim worse..it would be hard to swim with the gear half on and half off, the other problem is keeping it in place when paddling...the forarm elbow is tough to keep in place...the balance between to tight or to lose on velcro adjustment is very small....to tight and your hand and arm goes numb...to lose and it slides down onto your wrist..
Hard plastic armour has it place...,but there are newer high tech soft armour system on the market, that works as well if not better than the hard stuff, and because it is soft can be worn under your dry - splash gear, were the current can not get to it.
The European have developed impact standards for body armour. ...most motoport armour meets ce level 1 certification....level 2 cert a higher standard is currently only available for spinal protection.
I have found that the 3 companies make soft armour that works very on the river.
The lower armour from crash pads...they are out of utah I think...There gear has NO ce cert...,but works well for river use. They make tights with shin, knee, thigh, hip, and tailbone protection I personally use this gear under my dry suits. Cost is about $90 for a pair of tights...they also make upper body jackets that have spinal, chest, shoulder, elbow forarm protection. ..http://www.crash-pads.com....last
season I ordered 4 pairs of their mesh tights for myself and some buddies they added shin pads for us..we all like our gear.
My second choice would be the bohn armour...I have not used there gear, but I have heard good things...it is ce rated (I believe ) and cost only a little more than crash pad gear...
thing here is you can order the top and bottoms with only the armour you want and save some $ ...by example no need for spinal or chest protection the pfd has that...so order a shirt with only elbow forarm, and maybe shoulder armour.
My 3rd choice would be forcefield. ...very cool tech multi layer energy absorption gear....I use their tights when riding....but this is expensive tights are like $300...on advantage of this gear is that pads can be removed or inserted as needed.
Stay away from the d30 armour products...this stuff is negatively affected by cold temps...if you run in cold water rivers, this stuff gets very hard and uncomfortable...
I hope that this info is helpful to you.