Where do you got that from? Preparation for Sealion was actually underway, including rebuilding of ships. There was no report I know of listing the lack of trained personell as an issue.
Please state a source.
http://www.johndclare.net/wwii6_sealion.htm#part6
When used as a landing craft, the barges, tugs and motorboats required extra crew. In total, the Kriegsmarine estimated that a minimum of 20,000 extra crew would be needed. That's 20,000 extra crew at least knowledgable of matters maritime. By stripping its ships to the minimum (which doesn't bode well for the Kriegsmarine if it is required to fight a fleet action), the Kriegsmarine was able to supply 4,000 men. The Wehrmacht and Luftwaffe transferred 3,000 men who had been sailors in civilian life, and an in-depth trawl of the reserves and the factories and the drafts brought forward another 9,000 men. After digging through the entire manpower cupboard, the barges were still 4,000 men short of the minimum required.
Same here - source please.
http://www.johndclare.net/wwii6_sealion.htm#part6
Dowding had made preparations to pull 11 Fighter Group back to the Midlands in order to preserve an effective fighter opposition to an invasion proper.
Finally:
One single main exercise was carried out, just off Boulogne. Fifty vessels were used, and to enable the observers to actually observe, the exercise was carried out in broad daylight. (The real thing was due to take place at night/dawn, remember).
The vessels marshalled about a mile out to sea, and cruised parallel to the coast. The aramada turned towards the coast (one barge capsizing, and another losing its tow) and approached and landed. The barges opened, and soldiers swarmed ashore.
However, it was noted that the masters of the boats let the intervals between the vessels become wider and wider, because they were scared of collisions. Half the barges failed to get their troops ashore within an hour of the first troops, and over 10% failed to reach the shore at all.
The troops in the barges managed to impede the sailors in a remarkable manner - in one case, a barge overturned because the troops rushed to one side when another barge "came too close".
Several barges grounded broadside on, preventing the ramp from being lowered.
In this exercise, carried out in good visibility, with no enemy, in good weather, after travelling only a short distance, with no navigation hazards or beach defences, less than half the troops were got ashore where they could have done what they were supposed to do.
The exercise was officially judged to have been a "great success".
[...]
We can choose to wave a magic wand, and wipe out the RN and the RAF, and examine how successful the invasion was likely to be in their absence. Sandhurst has done this on four occasions to my knowledge. Both sides were given the historical starting positions, with an invasion date of 24 September.
In each case, the details of the fighting varied, but by each analysis resulted in 27 September dawning with the Wehrmacht holding two isolated beachheads, one at roughly 2 divisions strength on Romney March, and one of 1 division at Pevensey. Each were opposed by more numerous forces, with growing numbers of tanks and artillery. German resupply was still across open beaches.