Hiya, I'm a Dutch historian of political culture & national identity, and have extensive education regarding my own country's modern history.

As far as the 'bordering the Atlantic' goes one can make a pretty strong case that in premodern/early modern times bordering the North Sea pretty much meant being able to freely access the Atlantic. This gets more complicated as bureaucracy's grow, state institutions are strengthened and a foundation of intl. trade law is laid between 1600 and 1795. Before getting further into that I'll first try to elucidate the state of Dutch trade between 1400 and 1600.

For starters the Lage Landen or the Lowlands/Netherlands is a peculiar animal in the late Medieval era. Consistently suffering from overpopulation since the mid-1100s, Dutch and Flemish individuals fled their homelands to other parts of the Holy Roman Empire they were part of. Between 1150 and 1300 thousands of expatriates from the Lowlands settled in - among others - the German baltic lands, Brandenburg, germanic settlements in W-Poland, Croatia, and even Romania. These individuals usually were drafted through church institutions and forced to clear and work land that was previously uninhabited, cleared from their previous populations (as is the case with Brandenburg and the Slavs there), or just wilderness. These people would form the key of early trade activities in the Baltic, which was the initial 'local market' the Dutch traded in besides the Channel trade in wool and cloth troughout the Middle Ages. By the 1400s the introduction of new farming techniques, the consequent harvest surpluses, and consequent growth of market centres into cities helped concentrate large amounts of capital in the hands of the Burghers, now competing with the Clergy and Nobility for regional control. Building on the Baltic network the Burghers started exporting significant amounts of grain to Denmark, Sweden, Norway, and the German Baltic. In turn, from these places wood, iron, and fur was imported on a large scale.

By 1500 the city of Amsterdam had grown into a stapelmarkt or staple market for both the Channel trade as well as the Baltic trade with the West in general. The considerable wealth that this produced combined with the onset of religious troubles meant that the Dutch found themselves in bed with some of their former trade competitors, fighting their former markets off and on. With the formation of the Republic between 1568 and 1588 the wealth of independent and competing cities was concentrated into a formidable economy that could rival that of England and in particular Denmark.

As 1600 rolled around, the wars of religion still ravaged Europe, but provided the Dutch with a metric tonne of cheap conquests in Asia and the Caribbean. Through lying, stealing, privateering, invading, and blackmail the government of the Republic obtained significant overseas holdings in the New World, established a slaver outpost in present day Ghana, conquered coastal Ceylon, and sent expeditions into modern day Indonesia. In essence, the high-risk strategy of going all in financially in the religious wars rewarded the Republic with its maritime empire. In contrast to Sweden and Denmark (with their internal quarrels) this strategy played off really well and sustainably so. With this access by proxy, everything looked perfect by 1648 and the formalisation of the new European order in the Westphalian treaties. The ink was barely dry or the English and Dutch duked it out again, fighting 3 wars between 1652 and 1674. These wars - though largely lost/pyrrhic victories - produced several great statesmen and admirals that are an extremely important part of our modern state history. Examples include Witte de Witt, Michiel de Ruyter, Cornelis Tromp, and Adriaen Banckaert. The emergence of the Act of Navigation, among other things must be understood as key inflammatory elements in this rivalry.

Until direct Dutch meddling in English affairs in 1689 this status quo lasted. Having long competed with the English economically but not religiously, King-Stadtholder Willem III again seized a golden opportunity by marrying the protestant heiress to the throne Mary II (also his cousin) to form an Anglo-Dutch union, which could rival the power of Louis XIV's France. Upon Willem's death in 1702 Anglo-Dutch rivalry re-emerged, and with the declining trade-power of the Republic heralded new era of military competition. The Fourth Anglo-Dutch War in 1780-84 confirmed British naval hegemony, and effectively heralded the end of the pre-Napoleonic Dutch trade empire.

Beyond Napoleon's defeat at Waterloo (where Brits and Dutch for some inexplicable reason were again on the same side and seemingly not enjoying it very much) the Dutch trade empire was reinvigorated with the seizing of much larger swathes of Indonesia, the development of Caribbean possessions, and the agricultural inventions that allowed for output maximization both in the metropolitan Netherlands, as well as in Indonesia.

Much of the 19th century was spent in the shade of British ánd Belgian industrialisation; the Netherlands can only be seen as an 'industrialising nation' towards 1870 (compared to Britain nearly a 100 years ahead of that curve).

Between 1870 and 1940 (suffering heavily from the First World War by proxy) the relatively centralised colonial bureaucracy, indigenuous steel industry (w/ local coal), and passive military stance between 3 great powers, the Netherlands survived as a stable trading partner and producer of a wide variety of goods both local and colonial. Only abandoning the Gold Standard in 1936, the Dutch were involved in the emergence of the modern financial market and in combination with a comparatively large metropolitan population (around 10 million in 1940) kept a certain productive edge over smaller nations like Denmark, Norway, and Sweden.

In short; we just dominated trade a bunch; stole, lied, and bargained our way into the Atlantic without having direct land access to it.