It's a vig, so yeah - not water-tight. I don't have enough parts and shooting an enclosed model would be far more difficult.
Nuclear energy is very suitable for underwater use. First - its fuel has very high energy density, which means that recharging is needed only over very long periods of time. Second - it does not require air as fossil fuels do. So, it's a good choice for submarines ( most all modern are atomic ) and potentially, bases.
Amazing! I'm building a giant aquabase for my brother's B-day party next week. I'll put it up on MOCpages next week. By the way, the nuclear power data on the page is very ideal for the diorama. Nice job! 10/5