The INTp feels that the boat is sailing as desired as long as the INTp knows that there are no Te obstacles - the boat's machines are running smoothly, the water level will remain adequate, all the harbors will be open and with the desired supplies. As long as the information on such matters is satisfactory, the INTp is contented: the trip will proceed along the optimal flow.
The INFp feels that the boat is sailing as desired as long as the INFp knows that there will be no Fe obstacles. The INFp relies on the other people of the boat to assure that the trip will proceed well. As long as those people are well-disposed towards the INFp emotionally, the INFp is contented: the trip will proceed along the optimal flow.
The INTp is not particularly concerned with the other people on the boat. However, the INTp does need a trusted companion who will deal with them (if necessary) and will help the INTp to actually deal with the obstacles perceived by the INTp. That companion is the ESFp, who probably was also the one to get the INTp on board in the first place.
The INFp prefers not to deal with the kind of obstacles the INTp regards as vital: the INFp feels that the trip will proceed smoothly as long as the other people on the boat are well disposed. However, not everyone will be well-disposed towards the INFp. To the deal with those, and to the other obstacles that might arise, the INFp has an ally, the ESTp. And, again, probably it was the ESTp who got the INFp on board in the first place.
Depending on how you see it - - the ESXp is the bodyguard and guardian of the INXp; or the INXp is the navigator for the ESXp.