I have a lot of dogs in the boarding kennel that do this. Get what is sometimes called a "spaniel bowl" ... named because the sloping sides help to keep spaniels long ears out of the water. They sell nice big stainless steel ones at Walmart here. These are much more difficult, but not impossible, to tip.

I agree that it is NOT too early to start training. Tell her no when she starts to play in the water, distract her with a toy, and praise her when she diverts her attention to the toy. You can also start teaching the "Leave It!" command here.