IV Ativan, Dilantin or other barbiturate would be the usual medication "IF" the person was experiencing a series of seizures (Cluster seizures). There are 30+ types of epileptic seizures that vary in scope and severity. The Grand Mal/Tonic-Clonic are the most "stereotypical" type of a seizure. Diastat (Diazepam)is the other medical alternative and Diastat is administered, where the sun doesn't shine. If it was or is a single episode, that last less than five minutes, then no drug intervention is required.
When someone has a Tonic-Clonic seizure no restraint should be done except in the restraining the head and if the person is vomiting they must be turned on their side, if possible, to lessen the chance of aspiration. The area should be cleared as much as possible to lessen the chance of the person hitting something other than the floor. Do not put your hands in the mouth. A person having a seizure will not "swallow their tongue". They may bite it but it usually isn't severe. It is possible for the muscles in the airway to constrict and people have died from this but this is rare, and only in seizures of a long duration, and it is how the "swallow the tongue" idea was started.
Having said that: Any medical professional knows that a "single" seizure is not a reason for someone to be removed from a ship. The Captain, doctor and cruise line are showing incompetence and ignorance in this situation. I say this based on the information at hand and there may, very well, be additional information that we don't have that the doctor and Captain did. If this was a series of complex and/or cluster seizures then it would be a cause for concern.
I did notice that the Welsh press used the word "fit" to describe a seizure. I and many other people who live with Epilepsy don't have too much of a problem with this. There are some who do because they feel it minimizes the disease and adds to the stigma. I personally refer to the complex-partial seizures that I have as "flops" or "brain took a vacation". It is serious but not life threatening, in itself,and I stay "relatively" conscious during the episode but it usually requires drug intervention to stop it in a timely manner. Tonic-clonic seizures are not fun and dangerous because they come on, usually, without notice. I have not had one of those in almost three years and I'm glad of that. Kramer saved my butt on the last one of those because I was outside in sub-zero weather and his barking alerted my son about what happened.
I will say that Epilepsy has a stigma associated with it and many people can't handle seeing this and it can be as, or more, frightening to onlookers than to the person having the seizure. Because people have this reaction they do not want to be "uncomfortable" and isolate the person with Epilepsy. It is also embarrassing to the person with Epilepsy because they may wet themselves, vomit, salivate/spit or defecate during the seizure. No one wants to have people witness this but it is no reason to withdraw from life.
OK: I'll now stop babbling.