We don't really do the "fact check youtube videos" thing here, but I'm curious as to the actual claim being made: is the English coastline different from what exactly? There are multiple ports on both sides of the Channel that were considerable in medieval times but have silted up or fallen into disuse for other reasons, and the Norse raided down multiple rivers -- Kievan Rus' was founded by "Viking" groups, Paris was attacked by the Norse more than once, the entire county of Normandy was ruled by, well, the Normans, and so forth. Rivers were the highways of the medieval world, and warfare at sea was connected intimately with warfare on land.

I wrote about this in an earlier answer; I'll copy that below with some light edits.

What we know about naval warfare in and around Britain in, say, the period of the Norse invasions, is that ships were primarily used to move troops and their equipment around. There was no true naval warfare, if by naval warfare we mean warfare unconnected to war on land. Rather, ships were used to project power on the land, and the seas remained a debatable place. That meant that, on the one hand, there was little one could do to prevent an enemy landing troops on one's land, but on the other hand, one could equally as well count on using one's own ships and forces to force a landing on an enemy's coast. The scouting systems used at sea that would prevent that didn't develop before the 16th century or so.

When we see accounts of naval battles, they are universally fought inshore, usually in a bay, an estuary or even in larger rivers, and are usually fought as an auxiliary to a land warfare engagement. There were no missile weapons that could sink ships, and it wasn't possible to fit rams to the ships of the Norse and their imitators, so it was only inshore that grappling and hand-to-hand fighting could take place. Also, inshore communications were quick enough that they could on occasion call for help when a landing occurred, a prerequisite of getting ships together to fight.

Naval warfare in this era has been compared to mounted warfare on land: ships were a way to transport a group of raiders quickly to a destination and achieve strategic surprise. Shallow-draft ships could also carry raiders hundreds of miles into the interior of a country, using rivers for transport.

A scenario might be that a group of raiders has landed at a village, dragging their ships onto the strand, and that a counter-force manages to trap them with beached ships and burn their means of escape; the raiding force could then be hunted down on land. Many of the battles that we know about during this time period seem to take that form (the details of naval battle are very incomplete). Alternatively, there are some accounts of battles on the water between two fleets, where it seems likely that individual ships grappled with one another, with boarding being the decisive factor in their success. We do know that defense against ships in this era required a combination of fixed defenses (bridges, forts) and squadrons stationed at spots where they could quickly be called to respond. The accounts of battles that we do have tend to list a prince and his achievements (Alfred of Wessex went to sea with a "fleet" (sciphere) in 875, fought seven enemy ships and captured one ... etc.)

What we do know is that the type of ship used for warfare at sea in northern Europe was generally of the "longship" type, although the size varied by design. Ship-houses that have been excavated in Norway point to ships of maybe 80 feet long and only 15 wide, which accounts for them being called "longships" or "snakes." The size of those ships was measured in "rooms," being defined as the space between thwarts. The Skudelev 2 ship is a 25-room ship, about 100 feet long and 12.5 wide that would have carried probably 75-80 men (apologies for Wiki link).

Ships of less than 20 rooms don't seem to have been counted as warships, generally, and the size of a king's ships was bandied about in chronicles as a measure of his power. In the Norwegian fleet around the year 1000 or so, ships of 20-30 rooms were called "esnecca" or "snekkja," snakes, while those of 30 or more rooms were "drekkar," dragons, and considered quite unusual.

In terms of how Alfred was able to successfully defend against the Norse, fortified towns (burhs) were fortified locations, usually linked to settlements, linked by roads, that could command key fords or crossings; sometimes double-burhs linked by a bridge would bar passage along or across a river. Alfred teamed the burh system with a mobile army, mostly cavalry, that could quickly respond to attacks. It was similar to the system that Charles the Bald was developing in the Frankish empire, and one that Offa of Mercia had developed about a century before Alfred (Offa, though, lacked Alfred's purpose-built fleet).

The cavalry could alert nearby ships leading to small raids and ambushes that would occur when men had left their ships and their retreat was cut off by an arriving force. The Anglo-Saxon Chronicle has a description of such an action in 896, where a force of six Danish ships was raiding along the Isle of Wight. Alfred sent a force of nine ships to intercept them; when they found the Danes, three ships were beached with a small shipguard while the others were upriver raiding. The English ships attacked the guard ships and captured two of them, while one escaped, but in the process the English ships were grounded on an ebb tide, with only three of the ships on the same side as the rest of the Danish fleet and the other six on the other side. The Danes returned from raiding and attacked the three English ships, losing 120 men to 62 English killed. The battle ended when the rising tide re-floated the Danish ships before the bigger English ships, but only one escaped.