Hey Sarge - I use a float that I made myself. It is torpedo shaped with a hole in one end. I attach a 10m line (quite thick cord/rope for better handling) with a cast iron window sash weight that I found on the end.
I find that the weight acts like an anchor (we have swift currents here and a 9m tidal range...) so you can leave it wedged in a rock and the float sits in the current - good for a breathe up and for aiming for once resurfaced.
About one metre below the float is a carabiner (straight, not screwlocked) which used to have a bag on it (the last bass split the bag I am happy to say

) but now has a stringer on it.
I find that I can also use the float-weight for additional weight for stealth dropping. Just hold it and it carries you down without the need for finning (therefore less noise/ vibes inthe water).
A mate has a blow up/ inflatable Omer float with a diver down flag on it.
It is really really visible (larger and very obvious as to what it is - there was some confusion last month with my float and some windsurfers... but it was sorted out with speargun diplomacy).
Depends what you need to carry - we go out for around 2 hours and like to keep it minimal with gear in these tides.
Good luck - Ed