What's that 1 moment in gears of war?/which version is it

Idk if this is spoilers but like I'm tryna find that 1 game I played few years ago and in pretty sure it's gears of war from what I searched up and got in google

There was like this moment we were in a ship or smthing then some fish or smthing broke the ship apart in two and We could get this small gun with a saw function then fast forward alot there was a mech thing we could get onto and had to get to a objective or something? Can't rlly remember anything else except those sorry