I will try to make it short:
+ easy to learn and master
+ small, under 600 MB in size
+ decent UI, smooth controls
+ weather effects (rain), day and night cycles
+ atmospheric voice over (original speeches of politicians like Churchill etc.)
+ tutorials explain every ship class and its use
+ (campaign mode) ports get attacked by large fleets you can intercept, otherwise the enemy (re-) captures the port
+ free saving (except in mid-battle)
+ time slider
- heavily overpriced, it would be more fitting for a 4,99 EUR or even 2,99 EUR title
- rather dull gameplay, fights are basically the same over and over again
- random missions from HQ are meaningless and not worth the time reward-wise, you can completely skip them
- no special attacks or abilities for the ships
- no skills for your captain (although he obtains up to ten levels by gaining experience)
- the textures on the ship models are a joke!
- graphics in general not on par with a 20,- EUR price class title
- weather or daytime doesn't seem to affect combat in any way
- for all types of ships the sound of their engines and cannons are the same (A submarine roars like a battleship)
- the different ships do sometimes differ only in details, some have the exact same stats, just another ship model
- miserable AI regarding movement and shooting (even your own level 10 captains shoot like a blind man)
- SINGLE STRATEGY to win: Manually control a ship with long range. Then fight at long range, you win. Just don't let the enemy get too close and you will win by manually controlling where to fire at.
Make extensive use of the pause - function and manually control several ships, you are unstoppable.
You just get the enemy in range of your cannons, reduce speed, show him the side of the ship (so all of your cannons fire arcs can hit him) and fire away broadside after broadside, manually aimed.
(If you are lazy, just add carriers to your fleet and let them do their job automatically. You just care for the more dangerous enemies and take them out manually. Meanwhile, your carriers will deal with the rest.)
This game is quite fun for a while, but heavily overprized for what you get. It lacks a deep gameplay. The strategy to win is primitive. Fights get boring and repetitive once you get the idea.
For 4,99 EUR it would not be a loss, but the price of 21,99 EUR made me write this review.
If you unconditionally love naval warfare action-RTS (no simulation!), perhaps you will enjoy this for a while. Otherwise, don't touch it.