We are travelling from Venice to Croatia and due to getting sea sick, would like to travel by train, bus or car. Please advise the best method of transportation without taking a ferry. We can also fly. Time frame...August/September.
Croatia has many airports - where are you heading for? How much time do you have?
A useful starting point for route planning is rome2rio.com. Direct connections by air can be limited, depending on where you are heading and your precise travel dates.
Hiring a car with a one way inter-country drop will be very expensive - I have seen fees of 1,000 euros mentioned on this forum.
If public transportation looks awkward for your first Croatian destination, you can check out the possibility of shared-shuttle service. I've seen some positive comments about GoOpti on this forum, and there may be a competitor or two. I've never used any such services myself.
It depends on where you want to go and how many days you have.
To add to my previous post, I think best to get hire car when you arrive in Istria, this gives you full control of your travel places and times.