Sloeber -- I've also raised this question on nearby dive sites in Thailand as I'm also not so fond of long boat rides or spending the whole day on a boat. I would suggest if this is really crucial for you that you go somewhere like the Philippines instead where the sites tend to be a lot closer to shore (just a few minutes by boat). For example a place which I really enjoyed and didn't require long rides was Puerto Galera. We did three dives a day and all were amazing.
Or I'm sure you have already heard about places like Sipadan, if you are more concerned with getting in as many dives as possible.
Or I'm sure you have already heard about places like Sipadan, if you are more concerned with getting in as many dives as possible.