Originally Posted by T. A. Gardner

We've been thoroughly over this ground here, and I know of many other boards where Seelöwe has been discussed at lenght. The conclusion reached every time is that it would have been an unmitigated disaster for the Germans.
But, let's recap the situation briefly:

The German plan was to land one regiment from each of nine divisions on three seperate beaches seperated by miles from one and other with the invasion fleet leaving Bolougne, Calais and, Ostend / Antwerp. The initial wave was to take approxmately 96 hours to completely cross and another 72 to get ashore. That equates to ONE WEEK just to land the first wave! This puts the equivalent of just one weak infantry division ashore on each beach.
The one available parachute division was to land behind one of the beaches over a period of about 2 days (the Luftwaffe could only lift about half the division at a time).
With no, nada, none, zip, opposition the Germans could realistically expect to lose 30 to 50% of the landing barges just through beaching them.
The invasion force had little more than a motely collection of motor minesweepers, armed trawlers, and small gunboats for escort with virtually nothing bigger than a 3.7cm AA gun for armament. Many of the barges would have mounted 2 or 3.7cm AA guns. The majority of the crews operating the barges had little or no sailing experiance.

The Royal Navy had 36 destroyers, and about 400 small craft committed to immediately countering an invasion crossing. There were 26 1/2 divisions in England of which about 13 were fully equipped and manned. One was a fully equipped armored division. There were also 6 tank brigades and a number of independent infantry brigades and battalions in existance. The Home Guard numbered about 250,000 men and most had at least basic small arms and a bit of training.

The air situation was that both sides were roughly even in strength and capacity. The British early warning system (eg., radar like CH, CHL, CD and other sets) would have given plenty of warning of the approaching invasion among other systems. Surprise was going to be virtually impossible for the Germans to achieve.

The Germans had nothing beyond a vague plan to return the invasion ships back to France, reload them, and send a second wave across about 10 days after the first wave landed. Of the ports the first wave was obstensively to capture none was capable of supporting much more than a division or two in size.

Basically, from these very bare facts one can see the absurdity of the German plan. They would have tried and it would have been a catastrophic disaster.