The Royal Navy most certainly did have control of the sea, and the channel BTW. The "pocket battleships" (not even battlecruisers), Lutzow (ex.-Deutschland), or Admiral Sheer would be of little aid, the Graf Spee was lost well before the planned Operation Seelowe (but they were only 16,000 + tons). Maybe you are thinking of the Scharnhorst, and Gneisenau both about 30,000 tons (but they cannot do the job since they had been damaged in 1940, and were being repaired from March, 1941 to Feb.,1942). Or maybe it is the Bismarck at 45,000 tons which is the only true battleship in the modern context which the Nazis had by 1941, and it was hunted down and sunk by May of that year. Its sister ship, the Tirpitz was NOT out of the Baltic until 1942, so neither could be of any more help than they were historically, absolutely zilch help since they were non-existent when Seelowe was planned. The Prinz Eugen could NOT be of any help since it wasn't even commissioned until Aug.,1940, and hadn't passed its sea-trials. Also it was damaged by a mine in early in its career in 1941. Then it was tied up in Brest after the sinking of the Bismarck for repairs, and made that mad dash with the Scharnhorst and Gneisenau in Feb., of 1942. So, people must be thinking of the ten destroyers and less than thirty U-boats that the Kriegsmarine had as seaworthy units by mid 1940 through early 1941! Against that HUGE and imposing sea force of the Nazi Kriegsmarine (giggle), with their little surface fleet and about thirty submarine vessels, the Royal Navy (in 1940) could ONLY put up the aging but capable warships; Ramillies, Resolution, Revenge, Royal Sovereign, Repulse, Renown, Queen Elizabeth, Valiant, Warspite, Malaya, Barham, Nelson, Rodney, King George V(end of 1940), Prince of Wales (May ’41), and the of course the Hood, by the time of its demise it was as near to a Battleship as most other craft of its size. Its deck armor was lacking, but due for a refit when she was sunk by the Bismarck. However the Battlecruisers Repulse and Renown at 32,000 tons, 30 knot speed, and six 15 inch main cannon, were more than a match for most Kreigsmarine surface ships afloat at the time. And let us not forget the RN’s eleven light cruisers, its aircraft carriers, its submarines or its 53 destroyers in the Atlantic alone, nor should the Canadian Corvettes be ignored either. Remember the time frame, with no Japanese attack against the Commonwealth until Dec. of 1941, after Barbarossa, the Brits may NOT have dispersed their other surface power as they did historically. Especially if Nazi Germany was really seriously attempting an invasion using its entire available ships. Good grief, the Kriegsmarine was a pitiful force until after early 1941 and then only when the U-boats really started to make a difference, but by then Operation Seelowe was abandoned, and Barbarossa being prepared for. During the summer of 1940 the Luftwaffe had no large, armor-piercing bombs, no operable aerial torpedoes, and no torpedo-bombers. It's kinda hard to sink ships without them. Even with advanced weaponry and opportunities of five more years of advancement they sank few RN warships. I believe the Royal Navy would indeed take LOSSES, but the record of the Luftwaffe against the Royal Navy is rather dismal for a pronouncement of prowess as some have expressed. In my mind, the Royal Navy would have UNDOUBTEDLY prevailed in defeating the Kriegsmarine supporting a Sealowe cross-channel invasion. There were some light cruisers which were sunk by the Luftwaffe around Crete and in the Mediterranean in general, but still demonstrative of the uphill battle the Luftwaffe would face trying to stave off an earnest Royal Navy interdiction of Seelowe. Total; warship losses at Crete were 3 RN cruisers and 6 destroyers with another 12 warships damaged but repaired. Sadly for those who wish to "glorify" the Luftwaffe, it was a real dullard compared to its Japanese counterpart in sinking ships. And, the Crete campaign is the most likely similar scenario and outcome to Seelowe with the Royal Navy doing its job, and prevailing on the high seas, but at some cost in terms of light ships. A cost easily borne by a seagoing nation ardently defending itself and at the same time cranking out new ships aplenty.