[3] They have short, but sharp mandibles and immediately upon biting, they deliver digestive enzymes into prey to suck their liquefied remains.

[4] Like most other water beetles, adult Dytiscidae have an oval habitus, often tapering toward the head with the pronotum widest at the base.

The head, thorax, and abdomen are all streamlined; that is, they are integrated into a single, overall cohesive oval, as opposed to the three visibly articulate sections of some Carabidae like Brachinus.

[6][7] Diving beetles’ shape is optimized to ease navigation through water by reducing drag and improving stability while swimming.

[9] Like other water beetles, adult Dytiscidae get their oxygen while swimming by storing air in a space between their elytra and abdomen.

The power stroke’s function is to increase propulsion by means of maximizing the beetle’s cross-sectional area, which involves stretching the tibiae and tarsi and spreading out the setae.

In the recovery stroke, the beetle then reduces the water resistance by rotating its tarsi 90° and folding the setae.

[11] An ability specific to the smaller of the diving beetles is to rapidly blast ingested water out from the rectum.

Their taste receptors are concentrated on the maxillary and labial palpi, and they can detect sweet, sour, salty, and bitter chemicals.

This form of sexual signaling has been speculatively connected with the expanded antennomeres seen in the males of many groups in Dytiscidae.

[13] From their pygidial gland, medium and large-sized species can secrete two types of substances: one a fluid and the other a paste-like solid.

Underwater, diving beetles apply them to sensitive body parts like spiraculi and subelytral tergal respiratory surfaces to protect them from water.

Chemically, the secretion-grooming paste consists of benzoic acid, a glycoprotein, and some phenols, particularly methyl p-hydroxybenzoate and p-hydroxybenzaldehyde.

When disturbed, diving beetle have the option to release odorous food residues from there to deter any organisms.

Small species do not have chemical defenses, so instead opt to avoid danger by reducing their activity underwater or dispersing themselves when in groups.

Select Hydroporinae species live in terrestrial habitats, such as dry forest floor depressions, at least in the adult stage.

Some species in Africophilus, Agabus, Fontidessus, Hydroporus, Hydrotrupes, and Platynectes are specialized for living in hygropetic habitats.

Examples of interstitial species include Exocelina saltusholmesensis, Agabus paludosus, and Hydroporus bithynicus.

Remnants of C. explanatus were found in prehistoric human coprolites in a Nevada cave, likely sourced from the Humboldt Sink.

In the Guangdong Province of China, the latter species, as well as C. bengalensis, C. guerini, C. limbatus, C. sugillatus, C. tripunctatus, and probably also the well-known great diving beetle (D. marginalis) are bred for human consumption, though as they are cumbersome to raise due to their carnivorous habit and have a fairly bland (though apparently not offensive) taste and little meat, this is decreasing.

[29]The greatest threat to diving beetles is the degradation and disappearance of their habitats due to anthropogenic activities.

For example, species such as Rhantus bistriatus and Graphoderus bilineatus went extinct in Britain likely because of the drainage of the Whittlesea Mere.

Their flourishing started after rice producers switched from the conventional method of draining the land midseason while it is flooded, to no-till.

[33] Dytiscid adults are eaten by many birds, mammals, reptiles, and other vertebrate predators, despite their arsenal of chemical defenses.

Although the larvae of a few dytiscid species may become apex predators in small ponds, their presence is also often incompatible with fish.

In the European Union, two species of diving beetles are protected by the Berne Convention on the Conservation of European Wildlife and Natural Habitats, and thus serve as umbrella species for the protection of natural aquatic habitats: Dytiscus latissimus and Graphoderus bilineatus.

According to the narrative, upon finding nowhere to rest in the "liquid chaos" the beetle brought up soft mud from the bottom.

[27] The effect of that habit has not been tested, but it is notable that the pygidial and prothoracic defense glands of diving beetles contain many types of bioactive steroids.

[35] Beetles in these two families are known as “yewha inat” (mother of water; Amharic የውሃ እናት[36]) in Tanzania and rural regions of Ethiopia.

Meanwhile, in other areas of East Africa such as Zimbabwe, diving beetles are an aid for boys learning to whistle.