When one does not have time to make a proper eye splice, common practice is to use a bowline; but, a bowline halves the strength of the line and is thus suboptimal, however convenient.
There is a popular fishing knot, called the duncan loop, which is purported to preserve 95% of the line strength, and I'm wondering if anyone has used, or has any opinions about its use in lieu of a splice, as it can be quickly tied without tools, and can even be used with a thimble to prevent chafe.
The key difference that I can see between a duncan loop and an eye splice or bowline is that the loop will almost surely constrict with use over time, and as such, under significant load it's really more of a bend than a loop, but if a thimble is used, that could be a non-issue.
Though that raises the question of whether a thimble might reduce the strength of the knot, and perhaps a perfectly round thimble might be better than the typical teardrop shape.
Here is one tied with 10mm line:
Given that it is as strong as an eye splice, and can be made more quickly than a splice and without tools, one might wonder why splice at all? Cosmetic arguments aside...