It's not often I have seen a product as bad as the Garmin Colorado 300 GPS.

Although advertised as IPX7 Waterpoof mine died on the very first day of a boating holiday. The weather was rough and there was a lot of spray flying around for several hours, but the exposure was nowhere near close to what I am used to subjecting my old Garmin GPS 60 to. I had that unit strapped to the front of a Sea Kayak for fours weeks on one expedition, and despite being constantly soaked and occasionally submerged it withstood the abuse perfectly. Because the Colorado 300 uses a wheel to control the unit, using it inside a waterproof bag would be very difficult.

In the photo on the left here you can see in the battery compartment how the acid leaked out. It's also not just my unit, Google Colorado 300 Water Damage and you find other threads. Even the seal at the top of unit over the USB port appears much flimsier than the seal found on my old Garmin GPS 60.

I called customer support and they said they had received other complaints but their engineers had tested the unit and found no fault. They told me that they are NOT planning to change the design!

I bought the Garmin Unit for the Sea Charts of the Exuma Islands, and even though I ended up replacing wet leaking batteries on a number of occasions, it worked out OK. The unit's  software frustrated me constantly but after upgrading the firmware it's better. No wonder TomTom took top place in road navigation from Garmin, these guys really have no idea how to write software. Just installing the UK TOPO map I bought for £120 was a nightmare.

Here is a screen shot of the UK TOPO map near Ambleside in the Lake District taken from the Garmin unit:

Frustrated with the level of detail, which not only missed footpaths but even minor roads, I bought a SatMap.  For £500 I got both the SatMap and 1:50,000 OS maps of the entire UK. Here is a screen shot of the same area from them (the unit has a vastly superior 640x480 screen):

My SatMap has worked out fine and if it supports the maps you need I would definitely recommend it instead. I set my SatMap screen to timeout after a few seconds which gives a few days of battery life, and have not yet bothered with the routing logic so can not testify how easy to use that is.