Replacement battery?

I am going to need a new battery for spring. What type is the best for just an inboard ski boat – just starting?

What is the best brand/type to buy for a ski boat? I only get to the lake about 15 days a year. The battery sits unused the rest of the year. Is there a battery that lasts longer than others under these conditions?   Any advise on cold cranking amp ratings?

It is for a CC Mustang - Ford 302.

Thanks for the help.

No lead acid or gel battery will hold a healthy charge when used so infrequently. You should just go ahead and get a marine cranking battery (NOT deep cycle). The marine batteries have stronger cases and internals to withstand the pounding. At least once a month, you should put a charger on the battery and bring it back to full charge. Letting a battery discharge to low levels does it lots of harm. You might want to consider a solar trickle charger that can be left in place during periods of non-use.