Why was the Enterprise parked at the bottom of the ocean? Kirk and crew wanted to stop a volcano from destroying a planet. Why did this necessitate bringing the Enterprise inside the planet's atmosphere?
I know size of the ship is still being fiercely debated but at 725 meters from the official source. That makes it larger than the Enterprise-E from TNG. With a ship that size, what was Kirk thinking putting it in a situation where it can be exposed like that. It's not like the transporters or shuttlecrafts weren't operable.
The sketch of Enterprise and most of the proportions are wrong. Here's a better one...