I am getting unlimited next week. I can join in almost anytime during summer break.
As far as stratgy goes, watch out for wave : 8, 13, 14-15.
Wave 8 is when the first massive fleet hits. There'll be tons of war sloops, war gals and war frigates.
Wave 13 is the same, but they have even more HP. While many disagree about using mines here, I think you really do need them. When fired into a straight line in front of a warship, it can pretty much sink them instantly.
War sloops and gals : 4-5
War frigate : all 6 mines.
Wave 14 is just a complete pain. Tons of light sloops with rediculous HP and speed. I usually start with a vertical line of mines, then make a second line after the first fleet passes (they will actually dodge the mines if there are gaps in between!). Usually lines of mines at the very right where the ships spawn and keg in the middle work well. Then just rotate between Scattershot and round, or cold shot if anyone gets any.
In later waves, there are also fleets that shoot like 500 fire barrels at you a second, which almost perma-knocks you down. Target shot is actually very effective during these situations. I'd suggest having someones in the group having some during later waves.
If you can get past these waves, the rest are just a repeat of these types but with more HP.