I have a small Furuno on my boat and it picks up everything. On a calm
day I track seagulls and logs. Its only when the sea surface is really
disturbed (25+knots and lots of fetch that the radar starts missing
small boats.

Having driven large ships, I would say that if they are watching their
radar, they will see you even in a small fiberglass boat unless the sea
state or weather is such that clutter is a problem