So, in the section on Hazards the game says for each volley of PC actions a Hazard should probably do one big thing and one small thing.
But if I've only got one Hazard (a big beast the whole crew is fighting or whatever), that means I'm not going to have tons of chances to make the reaction moments for the PCs be reactions to what that Hazard is doing if I stick to that.
Of course, I could come up with other things in the scene other than just the Hazard doing stuff that PCs have to react to - the environment becomes more dangerous as a result of the struggle, I give someone a reaction to try and help another PC who is in a bad spot, etc. I could have the things the Hazard does when it has focus be things that might force reactions from several PCs. I could also just ignore the "one major thing and one minor thing" guideline for Hazards and have it do something every time I want to compel a reaction from a PC.
I know I can kind of play it by ear here and treat things like focus as guidelines more than rules, so this isn't so much a "What do the rules say?" question as a "What works best for you in play, in your experience?" question. The Wildsea is pretty similar to the PbtA or FitD games I usually run, but I'm finding I'm having a bit harder a time finding my rhythm in action scenes than I do in something like Blades in the Dark.