Free RPG day. River environment countdown with combat.

1) Combat and countdown are happening at the same time, correct?

2) Eelgators all at once (feels overwhelming) or drop one in everytime I get the spotlight (felt like a cakewalk)?

3) How do I interweave countdown timers with combat?

4) If I was supposed to reward hope / fear on all of those countdown rolls, everyone would have been full up.

I really need more examples of play for things like this.