A B737; NOT EQUIPPED FOR OVERWATER FLT; DEVIATES MORE THAN 50 NM OFFSHORE WHILE AVOIDING TSTM ACTIVITY ON THE MRLIN 4 ARR INTO FLL; FL.

Narrative

WE WERE ON THE MRLIN 4 ARR TO FLL. WE WERE HEADING EASTERLY; INSTEAD OF SOUTHEASTERLY AS IS NORMAL ON THE OMN-TRIPL SEGMENT. THIS WAS DUE TO A LINE OF TSTMS OFF OUR R (S) OF US. WE WERE PARALLELING THE LINE. THERE WAS A SMALL OPPORTUNITY TO TURN S IN BTWN 2 CELLS; WHICH WAS MISSED. I REQUESTED A 60 DEG R TURN; BUT ATC KEPT SAYING 'YOU ARE CLRED TO DEV E;' DIRECT TRIPL WHEN ABLE. WE THOUGHT THEY MIGHT LET US TAKE A SHORTCUT TO DUBBL -- WE BOTH THOUGHT THEY HAD SAID DIRECT DUBBL WHEN ABLE. BUT WITH THIS CONFUSION WE CONTINUED E. IF WE HAD TURNED S TO GO BTWN THE 2 CELLS; WE WOULD HAVE HAD TO TURN N TO GET BACK UP TO TRIPL. WHEN WE WERE APCHING THE LAST CELL OFF OUR R AND WERE GETTING READY TO GO AROUND IT AND HEAD SW; ATC ASKED IF WE WERE OVERWATER EQUIPPED. WE SAID NO; AND HE SAID THAT HE SHOWED US MORE THAN 50 MI OFFSHORE; AND THAT HE DIDN'T THINK THAT WE COULD DO THAT. I SAID THAT WE COULDN'T FLY INTO TSTMS. AT THAT TIME WE WERE TURNING R TO GO AROUND THE LAST CELL AND HEAD BACK TO LAND. I BELIEVE WE TOOK THE SAFEST COURSE OF ACTION -- AVOIDING THE TSTMS. I KNEW THAT WE COULD EXCEED THE 50 MI LIMIT FOR WX; BUT I DIDN'T REMEMBER UNTIL LATER THE PART ABOUT DECLARING AN EMER. AS IT IS; THE ARR HAS YOU 35 MI OUT TO SEA; AND WITH ANY WX ON THE ARR; THERE IS NOT MUCH DISTANCE TO WORK WITH. AS I DON'T WANT TO HAVE TO DECLARE AN EMER IN THE FIRST PLACE; IN THE FUTURE I WILL QUERY ATC ABOUT OUR DISTANCE FROM SHORE; TO WAKE THEM UP TO THE POTENTIAL PROB; AND SAY SOMETHING LIKE 'IF WE CONTINUE ON THIS HDG FOR 20 MORE MI; WILL THAT KEEP US WITHIN 50 NM OFF SHORE? IF NOT; CAN WE TURN W AND TRY ANOTHER ARR RTE?