Had two naval attacks playing as Spain from Great Britain yesterday...

The first wasn't particularly subtle - two decent sized navies took station off the coast of Florida for about 5 turns before finally declaring war and landing. Getting plenty of warning meant I was able to recruit some defenders, if only they had been smart enough to sail to say Cuba and land there.

About 10 turns later, after a temporary peace, Great Britain declared war again and landed an army next to Lisbon in Portugal. That one was unexpected, and it was a very close run thing to hold the city.

In both cases any ports in the area were defended, so the invasion was direct from the ships.