I think the discussion is going a little wrong. It's worth reading the article on operation sealion in Wikipedia on this much as that source is now severely corrupted.
Some facts about the modified barges to invasion barges and river ships (powered barges).
1 They were to be modified by cutting of the bow and attaching a ramp to drive trucks, tanks etc on and off. They also were to have concrete poured in to strengthen floors to handle tanks. Its a fairly daunting amount of modification work.
2 Square bottoms roll less in heavy seas than round. This is not a problem for barges.
3 Unpowered barges after landing tanks were to be marshalled and escorted back to France after 2 days.
4 Unpowered barges could be towed or pushed by either a river ship or the 400 tugs collected for operation sea lion.
5 Over 260 Panzer III and Panzer IV tanks were converted to 'tauchpanzers' or diving tanks. They were sealed and could drive along the ocean floor to a depth of 15m by way of a 16m air intake hose with an radio aerial. Apart from sealing the tanks had bilge pumps and rebreather escape systems for the crew as well as a gyrocompass and navigation system. I don't think these would have been dropped into water that deep, maybe 5m but they would be impervious to fire till they surfaced. They were actually used during operation Barbarossa.
6 The smaller Panzer II modified as a schwimmpanzer (with 20mm canon) would float via way of caissons and fire their gun during their swim ashore.
Dealing with the Royal Navy:
1 The invasion corridor would be cordoned off with a dense mine field from the Royal Navy.
2a Coastal Artillery, based in France, would also cordon of the invasion corridor from the Royal Navy out to much of the distance. The 8.8cm FLAK 37 is a deadly anti shipping weapon due to its fire control and ability to FLAK burst. I imagine 105mm, 6 inch, 8 inch and 11 inch coastal artillery would be set up by the German Navy (who had troops and division for harbour defence). That should protect the invasion fleet half way if not the whole way across the channel in some areas
2b Luftwaffe FLAK 37, FLAK 38 and FLAK 39 8.8 cm, 10.5 com and 12.8 cm guns would be highly effective against shipping and craft.
3 Luftwaffe would have had time to reassess its performance at Dunkirk and change its anti shipping attack methods.
We KNOW they became effective. Briefings, notes to crew and a little bit of practice against towed targets. They will learn quickly and they will also be undistracted by campaigns elsewhere.
4 One thing I need to research more is the state of German radar in mid 1940. Seetakt Shipborne radar was definitely available on anything from destroyer up plus a few of the larger torpedo boats. SeeArt (See Artillery) is essentially Seetakt converted for coastal anti shipping use, FuMo 1 Calais A and B and FuMO 2 Calais.
The shore based Seetakt peformed better than ship based because it had a larger antenna, more powerful transmitter and could afford more complicated circuitry that didnt require the same lever of minurisation, marinisation and shock resistance.
This means that a few radar equipped Kriegsmarine ships half way across the channel can detect the Royal Navy and either open fire using night vision optics or illuminate with star shell or search lights while smaller craft attack. The shore based artillery would take care of the rest.
Achieving Air Superiority.
I don't see this as a matter of strategy or tactics by the Luftwaffe. The Luftwaffe didn't have the right equipment.
Required would be the following:
1 All Me 109 and Me 110 equipped with ability to carry a jetisonable fuels tank or a bomb with the necessary modifications to the altimerter (altitude alarm) and Revi Reflector sight (second reticule for the toss angle). The Me 109E4B and Me 109E7B had this facility as the BoB ended and would have been available in fair numbers. It was needed before the BoB stated. The earlier Me 109E1B could carry a bomb but no drop tank. (fixed drop tank for ferrying only)
The additional range should increase penetration depth 60%, it should increase the area of Britain under which the Luftwaffe operated fighters by 2.5 and it should double or treble the number of Luftwaffe fighters over the UK.
2 The Focke-Wulf Fw 187 with DB601 engines and 1300 Litres internal fuel needs to be built, if necessary by sacrificing an equal number of Me 110, around half the force.
It is NOT correct to say that the Fw 187 would not be an excellent dog fighter. Manoeuvrability depends on power to weight ratio of the twin engine aircraft being the same or better than a single fighter. The Fw 187 had that. Wing loading is important but a larger wing may reduce turning circle will also reduce speed so its a trade of.
The Fw 187 would have had far better speed than Me 109, Spitfire and about 65%-70% more range. Likely enough to roam over half of Britain.
3 A high speed reconnaissance aircraft is needed. Either unarmed, unarmoured Me 109 or the Fw 187 to gather intelligence.
RAF losses would be higher, Luftwaffe bomber losses much lower.
Goodness, over a hundred men, unaccustomed to the sea, seasick and tossed around on flat bottomed barges trying to use their AA cannon and their infantry machine guns whilst running flat out at 9 knots against a flotilla of determinedly-captained RN destroyers does not look like good odds for the Wehrmacht.
Here's the most powerful barge intended for Sealion, the German
Siebel artillery support ferry.
View attachment 606451
Facing each of the few ferries will be a flotilla of RN destroyers.
View attachment 606452
And what about the
regular barges? These poor buggers will never make the beach.
That Siebel barge was quite stable and used not only as an armed barge but a landing craft. It was improvised using Army Pontoon Bridge Pontoons and this made it transportable by road an rail, hence it was used in inland lakes and seas and could be used for a river crossing before a pontoon bridge was set up. It could get tiger tanks across a water crossing.
The Siebel Ferrys had a draft of only 1.2m and a little calculation shows that with a 5m ramp (dont know what it actually was) would mean any solider or tank would find himself in 70cm of water assuming a 10:1 beach slope. Fording depth of a Standard Panzer IV at the time was 0.8m latter increased to 1.2 but i imagine special modifications would be made similar to the schwimmpanzer so that fording depth would be ate least half way up the turret.
Noe also the Kommandogeret 40 FLAK predictor. This computed a continuous firing solution so long as the men: the trainer, the layer(elvation) and range finder operator tracked the the targeted enemy ship. If the ship moved the solution would instantly update and the guns would repoint viag their guages If the 'ferry' moved due to swells so long as the layer/trainer maintained track and the fire order was given right it would hit. A RN MTB could be directly targeted by 30-45 rounds per minute of 8.8 cm fire either bursting above them or inside them.
Too powerful? The Germans didn't have that much experience bombing ships - yes, they could do it, Luftwaffe He 111s sank two of the Kriegsmarine destroyers at the beginning of the war, but against the entire Royal Navy? The Home Fleet destroyer squadrons had more destroyers than the Kriegsmarine's entire surface fleet and let's not forget that the 'RAF' is not just 11 Group Fighter Command squadrons, let's remember that 13 Group squadrons were largely out of reach of Bf 109s, so could (and did) operate with impunity against German bombers that ventured that far north. This meant that in the event that 11 Group in the south east couldn't cope, there were other units that could be relied on as back up - something the Germans failed to reconcile with and was the foundation of Park and Dowding's strategy of putting smaller numbers of fighters up at any given time to attack bombers (it worked, by the way). Let's also not forget that German torpedoes in 1940 were terrible and very rarely worked, and the number of torpedo droppers the Luftwaffe had available to it was small in 1940; the Luftwaffe had a total of 135 torpedoes available to it in March 1940, and by the end of September, 1/ Kustenfliegergruppe 106 and its He 115s had fired 16 torpedoes and reported only two hits, which doesn't equate to efficiency, so being realistic, this statement of yours is pure hogwash.
A Mine corridor and coastal artillery based in France greatly simplifies the problems the German Navy and Luftwaffe would face.
The Luftwaffe was clearly focused on land warfare. The problems at dealing with the Royal Navy evacuation at Dunkirk were clearly used as lessons learned and the Luftwaffe's anti shipping capabillity improved though it took improvements in equipment. It doesn't take much. A few officer would know, the Japanese might provide tips and the training material passed on. Bombs on the Me 109 would help as the 109 was successful of crete as an anti shipping craft. Destroyers are certainly difficult targets.
I suspect the Luftwaffe's main MTB and ship killer would be the Me 110 due to its frontal fire power and heavy bomb load as well as accuracy (as good as the Ju 87 during BoB)
If anyone has any pretensions as to whether Sealion was going to work, here's a quote from one of those involved in its planning and execution, one Heinrich Bartels, who was responsible for assembling the invasion barges at Dunkirk. During a visit by Raeder to the port on the eve of the invasion, he asked Bartels, "Do you think we shall make it across to England? Are you optimistic about it?"
Bartels, slightly taken aback by the questions from his superior, replied with, "Without optimism, Herr Grossadmiral, the thing will be a flop from the start..."
I worked in Germany in the early 1990s for a year. That's pretty much their sense of humour. It would have been said with a straight face. The laughs at the pub afterward.
The Germans planning operation sealion were intelligent, determined but knew they were up against it. They came up with a plausible plan and when the conditions of the plan were impossible to meet cancelled it.
It should be pointed out that for a nation absurdly accused of planning 'world conquest' the lack of long range aircraft, amphibious craft and the fact that they invaded the Soviet Union knowing they lacked the capability of invading more than 1/4 of the way in (they drew a vertical line to the limit of their logistical and opperational capability, the High Command and Hitler knew) shows something else was going on.