Hi Flyflicker, not being rude but haven't visited in a while.
I usually dive the south east coast and there is plenty of ground there for the kind of diving you are looking for. La Rocque is my favourite but green island, la hocq and la mare are also all good.
Depending on the amount of time you have getting in a good few hours before low tide will allow you time to get out to the back reefs and dive them at low water before riding the currents back in. if you are shorter on time then la mare may be a good option as you can be a bit more flexible getting in and out with the tides and its only 5 mins back to st helier.
feel free to PM me if you want any more detail.
I usually dive the south east coast and there is plenty of ground there for the kind of diving you are looking for. La Rocque is my favourite but green island, la hocq and la mare are also all good.
Depending on the amount of time you have getting in a good few hours before low tide will allow you time to get out to the back reefs and dive them at low water before riding the currents back in. if you are shorter on time then la mare may be a good option as you can be a bit more flexible getting in and out with the tides and its only 5 mins back to st helier.
feel free to PM me if you want any more detail.