Players are often faced with a single naval unit that seems to offer minimal usage, and decide they’d rather go ahead and eek what little value it offers out of it right now, rather than being patient.
For example, if through a combination of skill or luck the UK player still has his Indian transport a few turns into the game and Africa is already won by the Allies, the UK player may be tempted to just bring a couple of African infantry up through the Suez Canal and join in a larger attack that may be going on in the Ukraine or Caucuses.
However, while that may offer some marginal value right now, what is the German player going to do on his turn?
Two fighters and a bomber are going to easily wipe out that undefended transport and the potential threat it might have remained will go with it.
Consider instead that the UK player uses that transport instead to shuttle troops out of Africa and into Asia. Meanwhile, it sits there in the Red Sea, constantly posing a threat to Southern Europe that the Armada off the coast of England could never cause. The entire game, the Germans will be forced to keep a few infantry in Southern Europe as a result of that threatening transport. If it weren’t there, Southern Europe would be perfectly safe, and could be left completely empty, freeing up those troops for other duties.
Similarly, a US transport off the coast of Western Canada poses a threat to the Soviet Far East, not to mention Japan itself in a couple of turns (should the Japanese fleet decide to flit off to Africa).
So when you have a single remaining naval unit in a certain theater, resist the temptation to just throw it to the wolves, as you’ll often find it can serve a far better purpose just lurking around and waiting for its day in the sun.