Boat Stage optional mission

[waveshaper]

I'm having massive trouble doing the optional mission where you have to kill the boat demons before they reach your boat. Is the only way to do this the cannons? With them only being on the front boats, and the cooldown being so slow, I can only really kill around 5 before sunrise.

I also was able to kill one by shooting at an exploding demon which then took the boat with it, but I only saw one spawn like this.
I feel like I'm missing something

[gigastar]

it becomes much easier once you unlock the bow

[Palewing]

If you move on at bit, you get several upgrades/options that will make the optional objectives far easier.

[snovv.paris]

Use exploding arrow, if the first shot can't kill all, just fire another one. Two maxed out archers on each boat may help too.

[waveshaper]

I have the bow but completely forgot about the exploding arrow upgrade. Problem solved, thanks guys

[Dumb_bune]

get the explosive arrow upgrade

[Samseng Yik]

This is really easy once you know the objective.
I get guns and bow all position at the corner of each boats. (max upgrade)
Nothing come close