If you mean electical boxes like for plugs and switches there are covers made for those. Some come with the box,. Some are bought separately and look like a regular outlet cover plate but with a flap that covers the plug opening. Most hardware stores carry them. Kind of pricey if it's just a temp thing. The builder will provide them at some point. They also make solid plastic plates that are cheap, for interior use but I guess OK for temp, but not exactly weather proof.

I'm not sure what you mean by "water"...maybe holes in the wall for future hose bibs? You can stuff some plastic in there I guess, but shouldn't be needed. There are pipe plugs that might fit.

Hope your builder is OK with that. Having to remove stuff that wasn't needed can make some builders grumpy. People generally don't care for others "fixing" their work site. If these were suppose to be sealed the builder would have, should have, sealed them before they left.

Also, if there's a building inspection scheduled and the inspector sees what you did they may not understand and fail the inspection. Never can tell. That would make the builder more than grumpy.

Maybe a message to the builder explaining your plans first would be a good idea.

Thanks so much for your input! My husband says the covers go on when they put the actual electrical in. I will ask the builder, but he hasn't seemed as concerned as I am with water coming in the house. I understand the materials are made to withstand moisture, but it seems silly to let water come in when it doesn't NEED to and there are no other options.. (He put off putting all of the roof on for weeks due to heat and let it rain in multiple times). I will ask him but I usually make him grumpy no matter what. Thanks!