Who else tried that Flyfish tactic where you don't kill them but just break one launcher? It seems crazy, but it's actually very effective on hard waves and high tides. It's better having 3 flyfish with one launcher each instead of a new one keep spawning after you killed one.
Usually, on hard waves, boss keep spawning istantly unless there are 3 of the same type (yep, there can't be 4 bosses of the same kind at the same time!) so you can exploit this limit to block flyfish spawn and increase other bosses like Maws, who are easy to lure near basket.
Of course, if at the very start a flyfish spawn, i kill them asap. But when i notice more than one are already spawned, i just break one launcher and let them alive. With only one launcher they can aim at only one player at time, which makes easier to avoid the missiles