I was having a long chat with a supplier about Dairy Bleach today (I want to know what strength it is and he'll tell me next week). I reckon it's around 11-13% Sodium hypochlorite when fresh (it degrades over time). That's very potent! The catch for you is that the stabiliser in the mix is Sodium hydroxide, aka drain cleaner or Caustic Soda. It's not what you want on yer trailer, skin, clothes, etc.
I use a 12% product for work, it's top at cleaning moss and stains off brickwork when diluted down to around 10-15% from concentrate. I'd just be cautious around metals. If you're on a mooring, then it would work but the eco-types will be after you - the product carries watercourse hazard labels.
It's not toxic per se
, but will kill/dissolve everything it touches.