I guess we would call them whaleboats, but the Dutch seem to have an affinity for these double ended, mostly open boats called collectively Slopen.
In length they seemed to range from around 20 feet right up to this monster which was getting on for 40 feet yet was completely open, the family had erected the full length cover to provide cosy and private overnight accommodation. the welded steel hull looked as if this one might have been a former working boat or even a ship's lifeboat.
This was more typical a modern grp version, many of which were fitted with a low cabin forward. Typical for almost all the boats we saw was the wheel steering, presumably the cost and complication compared to a tiller are thought worthwhile.
A displacement boat ideal for the canals and rivers yet sea worthy and tough enough to take out on the open Ijsselmeer, compared to a modern high speed, deep vee hull form, these boats slip along with hardly any wash and presumably with reasonable fuel economy.