Posted by CalAbDiver on July 17, 2001 at 15:57:48:
1. definitely when abalone freediving, because it gives you something to hold onto between breath-hold dives, and something to put your abs into when youre successful (which should be always, if you choose a good site).
2. whenever there will be a significant surface swim from a beach entry, for added safety during the surface swim, and so that boats can see you better.
3. whenever there is a significantly deep descent, like over 35 fsw. this gives the divers a visual and a contact reference, so that if they have a problem on descent, they can slow or stop their descent.
4. whenever a safety stop is highly appropriate, giving the diver(s) something to hold onto besides kelp.
5. in some states, it is the law. you dont have a float, you pay a big fine. if your float floats away, you pay a big fine. you need a descent line for your float. 100' from the beach is often as far as you are allowed by law without a float.
it has nothing to do with whether you learned to dive with YMCA, NAUI, PADI, SSI, TDI, IANTD, etc. it has nothing to do with how long your OW1 class lasted. it has little or nothing to do with how much you have learned or how good you are.