You usually won't see them in rivers, unless you're near the shore where the water isn't moving as fast. But this summer, Oregon officials are cautioning vacationers to keep an eye out for possibly toxic algae blooms.

Blooms are large 'pads' or blankets of greenish-bluish 'goo' seen floating on the surface of lakes or ponds, especially where the water movement is minimal.

The Oregon Department of Health says as temperatures warm in spring and summer, algae blooms rapidly spread. Apparently conditions so far are prime for possibly bigger blooms this year.

The Department says while most are not harmful, some varieties can produce toxins that can sicken humans and kill pets. Most of us wouldn't wade or swim into one of these gross green slicks, but animals are another matter. Last summer, officials say several dogs actually died from toxins they ingested from algae blooms.

Advice from the Health Department? When in doubt, stay out,  of water that contains such paddies. Or, at least enter the water a far distance from the blooms so you won't have any direct or potential contact.  The Department has a map and information where toxic algae alerts are posted. But most Oregon waters are not routinely monitored so vacationers are advised to steer clear of the green goo.