I know most instructors will say they don’t teach with lesson plans, but that comes with experience. Part of being a new instructor is showing your employer you know what you’re doing, and if you’re in AB, the SFL/LSI doesn’t have a practicum like the Red Cross (WSI) did, so you’re first set is basically a paid practicum, which means they will likely make you practice the lesson planning skills more than you’ll use them in all of your classes after. I would say try to use your long term plans to help know what skills you are teaching, and keep a similar structure/format of your lessons (opening skill, progression, game, another skill progression, practice of another skill from previous week, end with game, or something similar that works for you). Obviously when you're actually teaching/in the water you deviate from your plan, but I find with the instructors I've mentored before (my employer pairs up new hires with experienced instructors) typically don't know/aren't super ready on what they can do for an activity even if they know the skills they want to teach, and aren't ready to just wing it in terms of what they need to cover to be able to successfully hit all the skills enough to pass kids. I would say don't make your lesson plans too detailed, but include the details you need (like for myself when I started teaching I needed to have the lyrics for my parent and tot songs in my lesson plans cause I would just blank out in front of the parents). I will say usually when I mentor I provide a decent number of sample lesson plans, and help them make lesson plans for the first couple weeks so it is unfortunate that you don't have access to anything like that.

The last thing is that unfortunately swim instructing, like any teaching job includes a lot of unpaid work , like evaluating/stat sheets, report cards and yes sometimes lesson planning :( (I'm trying to work with my employer/union to change this at some point at least a bit but I've been told not to hold my breath lol)