Welcome to the forums komoo. Good work on convincing your other half that a GPS is the ulitimate "safety accessory" for fishing and hunting.
There are others around here better qualified than me to answer your questions, but as no-one has jumped in yet, I'll have a crack.
You have slightly different requirements from a GPS for use in the bush and on the water. GPS reception is not so good under tree canopy or in narrow valleys, so you need a high sensitivity GPS. The other attributes I would look for are a clear colour display for reading your topo maps, electronic compass and barometric altitude sensors.
On the water, you're looking for a clear colour display for reading your marine charts, electronic compass and a marine mount (automotive works OK too).
Until recently, two good options for your needs would have been the GPSMap 60CSx (bush) or GPSMap 76CSx (marine). Either model would be fine for both uses anyway. Garmin have discontinued these lines and replaced them with updated models, GPSMap 62s (bush) and GPSMap 78s (marine). You can do a full feature comparison of the different models on the Garmin website.
I have used a 60CSx for both tramping and on the water (and in the car), and it works well for all these. When I've been in the bush with someone else who used a 76CSx, my 60CSx consistently maintained a better satellite lock whereas the 76CSx kept dropping out. The software on both is the same, but my preference is for the 60CSx as it is a rugged performer. But if $$$ are not a problem, go top of the line 62s. However, don't forget to budget some extra for topo maps and marine charts. Topo maps will probably cost from $150+, and marine charts from about $200+.
Last point - budget wise, the best bargain to be had at the moment may be a 60CSx if you can find one. Since the have been discontinued the prices have dramatically dropped in some places. That would be my pick, keep your eye out for a bargain.