seems to be some confusion here.
the term trainer and instructor is not interchangeable in rya powerboat qualifications
a powerboat instructor may have only a level 2 himself and may be qualified to teach just inland or both inland and coastal.
They may be able to teach rescue boat ticket.
An advanced instructor can teach level 2 coastal/inland and the advanced course and may be able to teach rescue boat.
Powerboat trainers is selected by the RYA from advanced instructors (with rescue boat ticket ) and invited onto a trainers' course run by the RYA itself. Those who pass the 3 day "perisher" course (horizontal snow during most of my first one)are appointed by the RYA to teach/assess prospective instructors at all levels-some of us also do training schools inspection.
After appointment we are "invited" to sample the delights of yet another trainers course on a regular basis-fail it, or not be actively teaching, and your appointment can be withdrawn.
I also share GEDs concerns over some instructors with no sea time in (see seperate thread).