Nice game overall, love the twist on the "diving" theme, very creative.
As mentioned by others, some kind of more obvious hit indication for when you hit enemies would be nice, was very hard to tell if the shots were actually hitting, even something like changing the colour of the eye temporarily would be fine
Gun upgrades were nice, and worked very well (especially enjoyed full auto bullet spray go brrr). Likewise with the speed upgrade.
Might be better to put the speed upgrade closer to the start, or somewhere more obvious, I found it right at the end, making it kind of useless.