I spotted this
The boat timetable from Santiago de la Ribera to the La Manga Strip.
Cost 4 euros each way
Outward 11.30, 13.30. 15.30. 17.30. 19.30. 121.30. 23.30. 01.00
Return 10.30, 12.30, 14,30, 16,30, 18,30, 20,30, 22,30, 00.30
The trip takes approximatly 1 hour and is just a ferry boat.
If you wanted to make it more interesting, then contact "OCIO EN MURCIA"
They do trips from Los Alcazares which stop off at the Isla Grosa (island grosa) and the boat has full bar service and a submarine vision tv!)