Yes it is one of the best but 2 coats are recommended. Note that Altex no5 Plus is now out, claiming 2 years performance with 2 coats. Whitworths don't have it on their website as yet - at least when I looked the other day - but it is advertised in the August Afloat.
It's worked well for me. 2 coats and then a 3rd around water-line, leading edge of keel and the rudder.

I'm not so good at photos. This is just shy of two years in the water after a 10 minute water blast.
It should be done more often than that. I just kept putting it off for another month or two to go sailing instead
Dived on it a couple of times just to clean the prop which I'd left bare last time. That was getting barnacles. I put propspeed on that this time. Very expensive stuff, but I'll see how that works.
The hull had slimy green film on it. Easily water lasted off. Aanti fouling annually or 18 months at a stretch would be the go.
2 coats and then a 3rd around water-line, leading edge of keel and the whole rudder for me.
I get 2yrs with Altex where i am, same with most of the locals as well. Done in late Sept, I'll dive on it maybe 3 times during the season (but never in winter, too cold for my bones, so just the waterline from the dinghy).
Talk to the locals where you sail, see what they use -conditions might be different.
We had a bloke move his boat down from years in Pittwater with a new coat of his regular AF, but within 8 or 9 months down here he was pretty badly fouled.
Don't know how to link this, so a pic.
Jode5 posted good reasoning behind the timing.

Thanks ...I been told by the guys at the Marina that they only use one coat with a roller then one around the water line, Second one I went too is saying the same.
this seem strange when so far everyone is saying two coats and one more around the water line
Thanks ...I been told by the guys at the Marina that they only use one coat with a roller then one around the water line, Second one I went too is saying the same.
this seem strange when so far everyone is saying two coats and one more around the water line
That is fine if your slipping once a year. It's all dependent on paint thickness. Using the right roller and not going back over the work will give an adequate thickness. I slipped my commercial fishing vessel once a year for 24 years and it got one coat and a doubling up on the waterline and leading edges.
To get 2 years with a yacht and save on slipping costs and doing the painting yourself then go two coats. First coat a different colour so you can monitor how it lasts.
Mark Barry-Cotter at Bay View Marina puts on two coats of Altex 5 as a standard anti fouling job at his yard.