I agree with "sailing dog." The knot needs to suit the situation. A
cleat hitch is foolproof - on a
cleat, but a round turn and two opposed half hitches would be my choice when tying to a post or rail. For a bollard, nothing beats a spliced loop of sufficient size to go round twice However well tied, I do not trust a bowline for mooring - or a clove hitch.
Cheers
Alan, Sydney