I cannot fail to note that, for a seaside boy like me, I do like infantry formations, specially in ancient times.
I love to depict, describe, and play with phalanxes (both classical and Macedonian), legions, and other similar armies, with mixed arms (light and heavy infantry, light and heavy cavalry, if available, and so on).
However, most of my novels (or novels-to-be, anyway) happen near, and largely, near the coast or in the sea. I can remind, off-hand, the 200 trirremes fleet of the Delian League in The Lybian, or the massive fleets in the Battle of Lade, in Revolt!. I guess I cannot avoid it: I like the sea, and I like to navigate.
I specially enjoy sailing. And sail ships are dear to my heart.
From the early merchant ships found in the Mediterranean in Bronze Age (dromon and other types), to the war galleys known to all (Phoenician and Greek galleys, for example), Egyptian sailing ships, Nordic merchant ships (the Hanseatic League) and then the host of sailing ships after the Portuguese Descubridores (whose English names I don't know, but you probably know the lot: naves, drakkars (et al.), carracas, caravels, galleons, longships, corvettes, fricates, ships-of-the-line, clippers, yatchs, schooners, xebecs, and a very long etc.)
Naval affairs have also have decisive (or at least "key") roles in many military events throughout History, including, for example, the Battle of Salamis (480 BCE), the Battle of Lepanto (1571 CE), the Battle of Trafalgar (1805 CE) or, in too recent times, the Battle of Midway (1942 CE), among too many others.
Many other naval events were probably more important than those above, and how many have I never heard of?
One that involved an important naval affair is the main subject of my First-Ever Historical Fiction idea, the novel I wanted to start writing and was afraid of, and it will be the subject of my Nanowrimo novel.
I won't say anything more for the time being (suspense! :-) but now you know I like sailing ships (my favourite among the ones I have been able to try is the dinghy "four-seventy" or 470, a two-manned monohull sailing ship, of Olympics category, which is really delicious to sail... :-)
Lastly, I can recommend anyone who can sail to do so: it's a really rewarding experience, where the beauty of nature and the harsh "bussiness" mix to produce a cocktail of sport and Zen-like relax that's hard to find.