[turtle]

Hi Tim,

It all sounds really well thought out. I would suggest going with the simplest option - if you have 2 kgs bottom weight, and a hefty buoy to lie over, you can pull up someone very fast hooked on to a 'biner. If you are diving in a group of 3, this is quite efficient. The biggest moment of risk for safety diving seems to be the time it takes to a, realise something is/has gone wrong then b,to act on that. Having relatively complicated safety plans that take an effort to set into motion just increases this risky period.

I don't know of any buoy-based counterweight systems that have ever functioned really satisfactorily enough to be really reliable and effective or worth the effort but i'm sure there must be some way of doing it properly that's not been done yet.

Anyway, those are my uninformed opinions. I'll be really interested to see what you end up doing mate.

Fred