I would totally take advantage of this water interest as it's something she enjoys, learns by playing with and is having FUN! There are so many water toys you can get for her that are low cost- if it's too hot outside, put the towels on the floor by the kitchen sink, bring up the step stool and let her have at it! I loved this water time with my kids- they were so occupied during this phase and I have some GREAT pictures! Plus, they both LOVE to swim when they were old enough for lessons.
So let her enjoy herself- be creative. Get some of the fizzy bath tablets so she can experiment with colors in a glass bowl. Jump on these interests that come up that will engage a toddler. Punishing her for being so naturally fascinated would be, IMHO, detrimental.
BTW, there are places like the Exploratorium in SF, Lawrence Hall of Science, Children's Discovery Center, YOUR BATHROOM, YOUR KITCHEN SINK, sprinklers out front, community water parks with run through sprinklers, etc. that you and your 3 year old would really enjoy.
Don't forget the sunscreen. ;)