Tips to build your fleet.

Well im really not an expert in fleets but i checked a lot of reports of the best players fleets.
Battle in sea is similar to the one in land. You can compare Front boats to batlle frontline(Steam giants and hoplites).
The back boats should be catapult ship cause they do the most damage(You can compare them to Battle back line(archers, sulfur carabineers,slingers).
So they grant you the extra damage.not a lot but its damage;) And usually who does more damage wins the battle.
Resuming, you should have a lot more of front ships in sea battles cause it does much more damage and once your front line is broken other boats take they re place and wil ltake tons of damage(this applys to ground battles to, more frontline than others)
In sea battles you have no flanks, thats a big difference.
To finish i talk about submergibles, You can compare them to balloon bombardiers. They grant a lot of damage to other boats(first they fight other enemy submergibles and then other boats. Subs dont fight alone)
You should have a fleet having lots of frontline(i use fire ships), some less back ships(catapults) and lots of subs too(Who has more subs has great advantage)

I leave too some examples of good fleets i see in reports:
(note that these ships i see in reports are ships in war situation so i dont need to have always such a large fleet i just post them
for you see what ships are better and the proportion you should build of each.)

Player Auror(CK)
140 flame trowers
40 catapult ships
66 paddle wheel ram
88 diving boats
(this is a huge fleet.lol)

Player Psio(CK)
350 Flame-thrower
74 Catapult Ship
69Diving boat

Griffin(Thorn)
146 Flame-thrower
36 Catapult Ship
38 Diving boat