Thank you for your reply.
It is possible that if your husband spent a long day on the beach in the sun, he could have had heat exhaustion. Too much sun can cause overheating. Symptoms of heat exhaustion are feeling nauseous, weak, having hot/cold sweats and chills.
Another possibility is that he is developing food poisoning, however, with no abdominal pain and no diarrhea, it is unlikely.
Finally, another remove possibility, however, the most serious one, is that he might be having symptoms of atypical heart attack. Sometimes heart attacks present themselves with nausea and chills. You don't necessarily have to have chest pains. With your husband's history of high blood pressure, it is a possibility.
I don't want to scare you, however, it is something on the differential list. I would suggest you call his doctor (who is hopefully in Hawaii) to discuss his symptoms. Otherwise, if he continues to feel unwell, I would suggest taking him to a local ER for an EKG and blood work (or call 911). If you have Aspirin available at home, give him 1 tablet.
I hope this answers your question. Please feel free to follow-up with any other questions you might have.