This was a simple game that does everything it tries to achieve which is great!
Personally I would like if the boat could turn a little bit sharper because I felt like I was fighting the controls the whole time, I can understand not being able to turn when staying still but I just wish it turned just slightly faster.
Any type of SFX would've also greatly improved the experience cause with no sound a game always feels very odd, even if its just grabbing sounds from freesound.org it can still help majorly.
The theme also only really seems to be through making it harder to save them all, but it is still technically possible, so I think there could've been some mechanic to make sure that theme shined through. Still, a fun little game though!