I think that there is a rechargeable battery pack for the G2/6P lights.
There used to be a NiCad one but it's been discontinued and pretty crap IMO.
If you want a rechargeable option for an incan Surefire:
Eg a G2/6P/Z2/C2/G2Z etc, pop out the P60 module, and insert a 9V/8.4V/7.4V lamp assembly, an example of one would be the P90, or go with Lumensfactory bulbs. Then insert 2X IMR16340s and you have a rechargeable incan 2cell light.
For something like G3/9P/C3 etc, insert 2X AW 17500 cells, and you have a rechargeable incan. It'll run on 3X Primary(non rechargeable) CR123A's as well.
For their C/P/G/Z LED's, rechargeable options are just as simple because the LED module even on the new 120 lumen heads are rated for around 6-9V.
Eg 6PL/G2L etc, just insert 2X RCR123A cells for rechargeable option.
Eg 9PL/G3L etc, insert 2X AW 17500 cells for rechargeable options.
IMO for fishing, you'd probably want something that's hand free like a head lamp.