The main ration in the Royal Navy during the period I study was bread, issued in the form of either biscuits (hard tack) or baked leavened bread (soft tack) at the rate of a pound a day. While ships ordered fresh bread to be used when in port, for seagoing purposes, biscuit was preferred because it would last much longer than fresh bread and was not nearly as difficult to make -- it was made of flour, water, and a tiny bit of salt mixed, rolled and cut, stamped with the King's broad arrow and baked. Workers using brick ovens expected to produce about 70 biscuits per minute (though this was not constant throughout the day -- brick ovens are heated by wood then used for baking until they cool). Each biscuit was specified to be baked at a size of "not less than five to the pound," that is each would weigh ~3.2 oz or 91 grams, approximately.

You're correct that it would not be easy to eat without soaking first, and it's also worth pointing out that the stamps in the center of the biscuit would be incredibly dense -- these were called the "purser's nuts," and stop giggling, because in this context they're referring to tree nuts. The usual method for eating biscuit would be to wrap it in cloth and pound it with something hard until it disintegrated, then add it to some sort of liquid such as soup or gravy, or even water to make pap to feed to invalids. Biscuit would grow moldy and infested if it got wet, leading to one of the worst puns ever, but as long as it was dry it kept well enough. If biscuit ran out or became completely unpalatable, a pound of dried rice could be issued in its stead.

Now, on to pasta: you're certainly correct that pasta can be made with much of the same ingredients as above, to wit flour and water, but most pasta also contains eggs and usually a bit of oil, so you can see how the price of making pasta would compare to the price of making biscuit. Plus, pasta is not a thing that would have been naturally made in Britain in this time period, and as I know from a fairly rainy camping trip, it will spoil as quickly as biscuit if it gets wet.

We do know that at least at some point the English navy ate pasta -- a letter from Drake's last expedition says the men were provided with

a certain victual in the form of hollow pipes … called by the name of macaroni among the Italians ...

(“Andrews, Last Voyage of Drake & Hawkins, p. 60)

For most of the above, I'm drawing on the work of Janet McDonald in Feeding Nelson's Navy.