Transportation options/ interest rates

There are  charters, cruise ships and  of course regular airlines - the main options. There are no  bridges,  not other means of getting here!  Other then that  I can tell you it is a long swim! 

Passbook savings account -  like  a daily savings account?  In pesos it pays almost nothing. If you are talking an investment account - depends on the duration and the amount of the investment. The rates are not as high as they used to be.

There is a ferry two times a week from Puerto Rico, but the fare is almost as much as a plane ticket from Miami.

Current CD rates on pesos accounts are from 6%-8% or so depending on amount, bank and time. Daily passbook is 3% or so and the exchange rate on the dollar is going up by at least that amount so you are lucky to stay even.

Bob K

The ferry that shuttles back and forth from Santo Domingo to Mayaguez, Puerto Rico is almost as much as a plane ticket as Bob K mentions.
The difference is you can get your own cabin, with a shower.
The trip is 12 hours. They have massive buffets, great music and dancing~night life and when you wake up in the morning you will be in Santo Domingo. It is a wonderful experience, well worth the money and a nice duty-free shop.