FenixLilly, there are plenty boats with OHII Full. Really plenty!
Your problem is you certainly have the rotating hydrophone wich works ONLY underwater...so you certainly miss plenty of contacts

You have to dive every 2 hours or so to detect something...and must admid it's frustrating/boring for myself too, when limited playing time.
I just navigate with the GHG one, wich is also historicaly accurate detecting on surface imo.