i've recently been fly fishing to this lake. I could see 4 big trout so I put directed the fly in front of them they kept looking at it but didn't take it why???? :confused:

If they are not in the mood, they won't. I have had this many times on shallow clear rivers. Sometimes if a trout is feeding on one particular insect e.g. buzzers they don't bother with anything else. Your best bet is to try different flies and see what works.

Cheers! I never thought of that.

Fact is that they've probably seen it all before and were a bit suspicious about your presentation, particularly if the water was very clear. Try using a long fluorocarbon leader and slow sinking fly like a small buzzer. Grease all but the last 6-8 inches so the buzzer hangs just below the surface. Dry flies are fun but I think cagey fish spot your leader lying on the surface. If you must fish 'dry' then a daddy or a hopper tend to work when the weather is very windy (like now!) and fish are picking up terrestrial insects blown onto the water.

If you are really keen lie down on your belly cos if you can see them they can see you. Also as Koicarp says if they are not in the mood they will just ignore. They may be where you can see them but that might not be where they are feeding. And as argyll states presentation can be, and more often than not is, key also, Just like floater fishing for carp really.