Keep moving with a purpose
Your cannons fire automatically, so your attention belongs on steering. Move into open water before the action becomes crowded, keep an escape route behind you, and avoid drifting into the edge of the battlefield without a plan.
A wide turn can be safer than a sharp correction. Give your ship room to change direction while keeping enemies inside your firing lanes.
Position the ship, not just the cannons
Damage matters, but a powerful shot is only useful when your ship survives long enough to take it. Read where enemies are gathering and reposition before they surround you. Use clear water to separate a large group into smaller threats.
Build for the battle in front of you
Upgrades let you shape each run. More firepower can clear enemies sooner, while defense and speed create breathing room. Choose a direction that solves your current problem instead of collecting upgrades at random.
If enemies are closing the distance, mobility or defense may buy more value than another damage increase. When you can already move safely, stronger cannon effects can help you control later waves.