Oops!
Deep water takes a bit of planning. Hit any water, even a couple of inches, too fast and it can splash around in the engine bay causing terminal damage. Get just a drop up the air intake and the engine stops dead with serious internal damage.
It's comes as no great shock then to find that water on a (probably) well corroded handbrake linkage was the 'last straw' for that item.
The starter motor, being fitted low, also got a soaking and, being an electrical item, did'nt like it at all.
There will be people coming up with all sorts of ideas such as plastic bags and water-proofing sprays, but to be honest, the only real answer is wade slow and shallow.
Book an off-road training course for a day and get some expert training on how to handle deeper water. It will save you money in the long run.
Good luck.