this is a very dangerous situatuin!
there are some scientific reasons for loosing power and steering:
when you drive through a poddle "rolling resistance " infront of the tire increases actually if you drive faster there is more rolling resistance force.,also there are adheasion force between tire and water, all these forces consume some engine power. you can imagine there is allways a wall of water infront of the tire, this water should escape through the tire threads to the sides or back of the tire, or trie go over it! (no other way)and the rate of escape of water through the threads is directly related to the depth and width and form of the tire threads and car speed, simply if water does not have time to go through the threads car actually floats on the water and you loose steering!!
they say tires with V shape or paralel threads provide better steering in puddles,
so tires should have enough threads,
all tires pressure should be set.
overcome with this water wall in front of tire consumes some engine power, if you drive with a constant speed from a dry road directly through a poddle you see speadometer obviosly drops some Km/hour.
another thing is that if your car has loose bushings, tierods, balljints,... in this situation highly contribute to loosing steering,
so I think first check the tires, then check the suspension for loose bushings,...
putting this aside there is another probability that: water penetrates wiring and engine components which causes engine does not work properly and loose power,...