Karl, i had an infection on a foot from a small cut ( i think i got bacteria in it from caladisi island where birds hang out) .. this one got serious. i had fevers, night sweats that soaked my bed and sheets and chills that almost vibrated me off the bed (dispite all the antibiotics i was on). I learned that a skin infection can spread to your blood... brain... etc.. can be lethal.

The good news is your thumb can be covered / proteceted alot easier than a foot (that gets wet when getting on and off a boat). there is a googlezillion of different bacteria in sea water so dont think that salt water is good for your thumb.

If i were you.. i would consider packing your thumb with antibacterial jell (neosporin). and wearing a surgical glove or at the least a thumb section to not allow crud in (taped shut). I would also wear new (sailing) gloves (avoiding bacteria in your old ones) maybe bring a few pair.

keep that hand out of the water... and i would think you should be good to go.

Disclaimer: i am not a doctor.. but i do live near a holiday inn